Exploring the uncertainties in the aviation soot–cirrus effect

A global aerosol–climate model, including a two-moment cloud microphysical scheme and a parametrization for aerosol-induced ice formation in cirrus clouds, is applied in order to quantify the impact of aviation soot on natural cirrus clouds. Several sensitivity experiments are performed to assess the uncertainties in this effect related to (i) the assumptions on the ice nucleation abilities of aviation soot, (ii) the representation of vertical updrafts in the model, and (iii) the use of reanalysis data to relax the model dynamics (the so-called nudging technique). Based on the results of the model simulations, a radiative forcing from the aviation soot–cirrus effect in the range of −35 to 13 mW m−2 is quantified, depending on the assumed critical saturation ratio for ice nucleation and active fraction of aviation soot but with a confidence level below 95 % in several cases. Simple idealized experiments with prescribed vertical velocities further show that the uncertainties on this aspect of the model dynamics are critical for the investigated effect and could potentially add a factor of about 2 of further uncertainty to the model estimates of the resulting radiative forcing. The use of the nudging technique to relax model dynamics is proved essential in order to identify a statistically significant signal from the model internal variability, while simulations performed in free-running mode and with prescribed sea-surface temperatures and sea-ice concentrations are shown to be unable to provide robust estimates of the investigated effect. A comparison with analogous model studies on the aviation soot–cirrus effect show a very large model diversity, with a conspicuous lack of consensus across the various estimates, which points to the need for more in-depth analyses on the roots of such discrepancies.

The Role of Analogy in Adaptive Explanation

<p>Cases of 'convergence' (traits which have independently evolved in two or more lineages) could play an important role in the construction and corroboration of adaptive hypotheses. In particular, they could inform us about the evolutionary histories of novel traits. However, there is a problem of causal depth in the use of analogies. Natural Selection's affect on phenotype is constrained by phylogenetic history to a degree that we are unfounded in projecting adaptive stories from one lineage to another. I will argue for two approaches to resolve this issue. First, by constraining our catchment area to closely related lineages we can control for developmental noise. Second, by integrating analogies into explanations which incorporate other streams of evidence or bootstrapping an analogous model across many instantiations, we can overcome the problem of causal depth.</p>

The Role of Analogy in Adaptive Explanation

<p>Cases of 'convergence' (traits which have independently evolved in two or more lineages) could play an important role in the construction and corroboration of adaptive hypotheses. In particular, they could inform us about the evolutionary histories of novel traits. However, there is a problem of causal depth in the use of analogies. Natural Selection's affect on phenotype is constrained by phylogenetic history to a degree that we are unfounded in projecting adaptive stories from one lineage to another. I will argue for two approaches to resolve this issue. First, by constraining our catchment area to closely related lineages we can control for developmental noise. Second, by integrating analogies into explanations which incorporate other streams of evidence or bootstrapping an analogous model across many instantiations, we can overcome the problem of causal depth.</p>

Exploring the uncertainties in the aviation soot-cirrus effect

A global aerosol-climate model, including a two-moment cloud microphysical scheme and a parametrization for aerosol-induced ice formation in cirrus clouds, is applied in order to quantify the impact of aviation soot on natural cirrus clouds. Several sensitivity experiments are performed to assess the uncertainties in this effect related to (i) the assumptions on the ice nucleation abilities of aviation soot; (ii) the representation of vertical updrafts in the model; and (iii) the use of reanalysis data to relax the model dynamics (the so-called nudging technique). Based on the results of the model simulations, a radiative forcing from the aviation soot-cirrus effect in the range of −35 mW m−2 to 13 mW m−2 is quantified, depending on the assumed critical saturation ratio for ice nucleation and active fraction of aviation soot, but with a confidence level below 95 % in several cases. Simple idealized experiments with prescribed vertical velocities further show that the uncertainties on this aspect of the model dynamics are critical for the investigated effect and could potentially add a factor of about two of further uncertainty to the model estimates of the resulting radiative forcing. The use of the nudging technique to relax model dynamics is proved essential in order to identify a statistically significant signal from the model internal variability, while simulations performed in free-running mode and with prescribed sea-surface temperatures and sea-ice concentrations are shown to be unable to provide robust estimates of the investigated effect. A comparison with analogous model studies on the aviation-soot cirrus effect show a very large model diversity, with a conspicuous lack of consensus across the various estimates, which points to the need for more in-depth analyses on the roots of such discrepancies.

Past variations of Lake Sevan (Armenia, lesser Caucasus): documenting climate triggers for the Near East and delivering insights for a sustainable management

&lt;p&gt;To understand the long-term patterns of atmospheric circulation in Eurasia, current paleoclimatic reconstruction syntheses lack accurate data for the Near East. In this semi-arid zone, precipitation is the key factor to be studied that strongly controls ecosystems and human societies. Few data are available from Lake Sevan (1900.52 m above sea level, 1,279 km&amp;#178;, 38.2 km&lt;sup&gt;3&lt;/sup&gt; as of January 1, 2021), the largest fresh-water lake in the Near East, whose past level variations may document seasonal to millennial precipitation changes.&lt;/p&gt;&lt;p&gt;We present here the preliminary results of the interdisciplinary Sevan-up Project. Its ambition is to develop a high resolution lake level reconstruction (which is expected to be preserved from the influences of long ecological processes and from human activities) and other climatic proxies (from pollen and molecular biomarker) in view to quantify precipitation changes during the Holocene.&lt;/p&gt;&lt;p&gt;The Early Holocene climate characteristics (strong seasonality) and environment (prevalence of steppe ecosystems) may raise an analogous model of future conditions in the Near East which will be affected by enhanced continentalism. The study of littoral and deep sedimentary deposits will potentially reveal the consequences of past variations in lake levels on its hydrodynamic functioning and trophic status. These results will give crucial information on how to improve the lake's water management&amp;#160;with the goal to reach a sustainable use and a better ecological state. Indeed, seasonal stratification onsets and trophic status dramatically changed since the man-made water-level fall during the Soviet times (40% of its volume).&lt;/p&gt;

Spectral wave energy dissipation due to under-ice turbulence

Dissipation within the turbulent boundary layer under sea ice is one of many processes contributing to wave energy attenuation in ice-covered seas. Although recent observations suggest that the contribution of that process to the total energy dissipation is significant, its parameterizations used in spectral wave models are based on rather crude, heuristic approximations. In this paper, an improved source term for the under-ice turbulent dissipation is proposed, taking into account the spectral nature of that process (as opposed to parameterizations based on the so-called representative wave), as well as effects related to sea ice concentration and floe-size distribution, formulated on the basis of the earlier results of discrete-element modeling. The core of the new source term is based on an analogous model for dissipation due to bottom friction derived by Weber (J. Fluid Mech, 1991). The shape of the wave energy attenuation curves and frequency-dependence of the attenuation coefficients are analyzed in detail for compact sea ice. The role of floe size in modifying the attenuation intensity and spectral distirbution is illustrated by calibrating the model to observational data from a sudden sea ice break-up event in the marginal ice zone.

SIMULATION OF REINFORCEMENT DEGREE OF NANOCOMPOSITES ELASTOMER/2D-NANOFILLER

Three schemes of modeling of reinforcement degree of nanocomposites polymer/2D-nanofiller with elastomeric matrix were proposed, differing principally from used ones earlier. These schemes do not used nominal characteristics of nanofiller (its modulus of elasticity, anisotropy degree), yet allow to obtain real (effective) values of these parameters. It has been shown, that modulus of elasticity of 2D-nanofiller aggregates in polymer matrix of nanocomposite is a function of stiffness of the indicated matrix. The other analogous model assumes the dependence of modulus of elasticity of 2D-nanofiller on its aggregation degree in polymer matrix, expressed by number of nanofiller separate platelets per one aggregate (“packet” or tactoid). The combination of these approaches allows to predict the real degree of nanofiller anisotropy and then reinforcement degree of nanocomposite. One more scheme uses the structure of nanofiller aggregates, characterized by its fractal dimension, for modeling of reinforcement degree of nanocomposites. The obtained real modulus of elasticity of 2D-nanofiller is in 5 orders of value smaller relatively to its nominal magnitude. The application of real (effective) characteristics of nanofiller allows to simulate reinforcement degree of nanocomposite within the framework of simple mixtures rule. Nanocomposites elastomer/2D-nanofiller are enough conservative systems, for which real anisotropy degree and structure of nanofiller aggregates do not depend on its content. This circumstance simplifies perceptibly prediction of mechanical properties of these nanocomposites.

CDK4/6 Dependence of Cyclin D1–Driven Parathyroid Neoplasia in Transgenic Mice

The protein product of the cyclin D1 oncogene functions by activating partner cyclin-dependent kinases (cdk)4 or cdk6 to phosphorylate, thereby inactivating, the retinoblastoma protein pRB. Nonclassical, cdk-independent, functions of cyclin D1 have been described but their role in cyclin D1-driven neoplasia, with attendant implications for recently approved cdk4/6 chemotherapeutic inhibitors, requires further examination. We investigated whether cyclin D1’s role in parathyroid tumorigenesis in vivo is effected primarily through kinase-dependent or kinase-independent mechanisms. Using a mouse model of cyclin D1–driven parathyroid tumorigenesis (PTH-D1), we generated new transgenic lines harboring a mutant cyclin D1 (KE) that is unable to activate its partner kinases. While this kinase-dead KE mutant effectively drove mammary tumorigenesis in an analogous model, parathyroid-overexpressed cyclin D1 KE mice did not develop the characteristic biochemical hyperparathyroidism or parathyroid hypercellularity of PTH-D1 mice. These results strongly suggest that in parathyroid cells, cyclin D1 drives tumorigenesis predominantly through cdk-dependent mechanisms, in marked contrast with the cdk-independence of cyclin D1–driven mouse mammary cancer. These findings highlight crucial tissue-specific mechanistic differences in cyclin D1–driven tumorigenesis, suggest that parathyroid/endocrine cells may be more tumorigenically vulnerable to acquired genetic perturbations in cdk-mediated proliferative control than other tissues, and carry important considerations for therapeutic intervention.

Proportional Relative Hazards Model for Competing Risks Data

In this article, we propose a Proportional Relative Hazards (PRH) model to differentiate subjects according to their risk for a primary event relative to competing events. The model estimates effects on the baseline ratio of the hazard for a primary event, or set of primary events, relative to the hazard for a competing event, or set of competing events (ω+ ratio). An analogous model is presented to estimate effects on the baseline ratio of the hazard for a primary event (or set of events) relative to the hazard for all events (ω ratio). A weighted regression method is introduced, along with practical presentation of risk-stratification using the PRH model in breast and head and neck cancer data sets.

The probability of intransitivity in dice and close elections

We study the phenomenon of intransitivity in models of dice and voting. First, we follow a recent thread of research for n-sided dice with pairwise ordering induced by the probability, relative to 1/2, that a throw from one die is higher than the other. We build on a recent result of Polymath showing that three dice with i.i.d. faces drawn from the uniform distribution on $$\{1,\ldots ,n\}$$ { 1 , … , n } and conditioned on the average of faces equal to $$(n+1)/2$$ ( n + 1 ) / 2 are intransitive with asymptotic probability 1/4. We show that if dice faces are drawn from a non-uniform continuous mean zero distribution conditioned on the average of faces equal to 0, then three dice are transitive with high probability. We also extend our results to stationary Gaussian dice, whose faces, for example, can be the fractional Brownian increments with Hurst index $$H\in (0,1)$$ H ∈ ( 0 , 1 ) . Second, we pose an analogous model in the context of Condorcet voting. We consider n voters who rank k alternatives independently and uniformly at random. The winner between each two alternatives is decided by a majority vote based on the preferences. We show that in this model, if all pairwise elections are close to tied, then the asymptotic probability of obtaining any tournament on the k alternatives is equal to $$2^{-k(k-1)/2}$$ 2 - k ( k - 1 ) / 2 , which markedly differs from known results in the model without conditioning. We also explore the Condorcet voting model where methods other than simple majority are used for pairwise elections. We investigate some natural definitions of “close to tied” for general functions and exhibit an example where the distribution over tournaments is not uniform under those definitions.