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The timing of Tibetan plateau development remains elusive, despite its importance for evaluating models of continental lithosphere deformation and associated changes in surface elevation and climate. We present new thermochronologic data [biotite and K-feldspar Ar-40/Ar-39, apatite fission track, and apatite (U-Th)/He] from the central Tibetan plateau (Lhasa and Qiangtang terranes). The data indicate that over large regions, rocks underwent rapid to moderate cooling and exhumation during Cretaceous to Eocene time. This was coeval with >50% upper crustal shortening, suggesting substantial crustal thickening and surface elevation gain. Thermal modeling of combined thermochronometers requires exhumation of most samples to depths of <3 km between 85 and 45 Ma, followed by a decrease in erosional exhumation rate to low values of <0.05 mm/yr. The thermochronological results, when interpreted in the context of the deformation and paleoaltimetric history, are best explained by a scenario of plateau growth that began locally in central Tibet during the Late Cretaceous and expanded to encompass most of central Tibet by 45 Ma.
In this work, we show how Gibbs or thermal states appear dynamically in closed quantum many-body systems, building on the program of dynamical typicality. We introduce a novel perturbation theorem for physically relevant weak system-bath couplings that is applicable even in the thermodynamic limit. We identify conditions under which thermalization happens and discuss the underlying physics. Based on these results, we also present a fully general quantum algorithm for preparing Gibbs states on a quantum computer with a certified runtime and error bound. This complements quantum Metropolis algorithms, which are expected to be efficient but have no known runtime estimates and only work for local Hamiltonians.
Theory of mRNA degradation
(2012)
One of the central themes of biology is to understand how individual cells achieve a high fidelity in gene expression. Each cell needs to ensure accurate protein levels for its proper functioning and its capability to proliferate. Therefore, complex regulatory mechanisms have evolved in order to render the expression of each gene dependent on the expression level of (all) other genes. Regulation can occur at different stages within the framework of the central dogma of molecular biology. One very effective and relatively direct mechanism concerns the regulation of the stability of mRNAs. All organisms have evolved diverse and powerful mechanisms to achieve this. In order to better comprehend the regulation in living cells, biochemists have studied specific degradation mechanisms in detail. In addition to that, modern high-throughput techniques allow to obtain quantitative data on a global scale by parallel analysis of the decay patterns of many different mRNAs from different genes. In previous studies, the interpretation of these mRNA decay experiments relied on a simple theoretical description based on an exponential decay. However, this does not account for the complexity of the responsible mechanisms and, as a consequence, the exponential decay is often not in agreement with the experimental decay patterns. We have developed an improved and more general theory of mRNA degradation which provides a general framework of mRNA expression and allows describing specific degradation mechanisms. We have made an attempt to provide detailed models for the regulation in different organisms. In the yeast S. cerevisiae, different degradation pathways are known to compete and furthermore most of them rely on the biochemical modification of mRNA molecules. In bacteria such as E. coli, degradation proceeds primarily endonucleolytically, i.e. it is governed by the initial cleavage within the coding region. In addition, it is often coupled to the level of maturity and the size of the polysome of an mRNA. Both for S. cerevisiae and E. coli, our descriptions lead to a considerable improvement of the interpretation of experimental data. The general outcome is that the degradation of mRNA must be described by an age-dependent degradation rate, which can be interpreted as a consequence of molecular aging of mRNAs. Within our theory, we find adequate ways to address this much debated topic from a theoretical perspective. The improvements of the understanding of mRNA degradation can be readily applied to further comprehend the mRNA expression under different internal or environmental conditions such as after the induction of transcription or stress application. Also, the role of mRNA decay can be assessed in the context of translation and protein synthesis. The ultimate goal in understanding gene regulation mediated by mRNA stability will be to identify the relevance and biological function of different mechanisms. Once more quantitative data will become available, our description allows to elaborate the role of each mechanism by devising a suitable model.
The zoom lens of attention simulating shuffled versus normal text reading using the SWIFT model
(2012)
Assumptions on the allocation of attention during reading are crucial for theoretical models of eye guidance. The zoom lens model of attention postulates that attentional deployment can vary from a sharp focus to a broad window. The model is closely related to the foveal load hypothesis, i.e., the assumption that the perceptual span is modulated by the difficulty of the fixated word. However, these important theoretical concepts for cognitive research have not been tested quantitatively in eye movement models. Here we show that the zoom lens model, implemented in the SWIFT model of saccade generation, captures many important patterns of eye movements. We compared the model's performance to experimental data from normal and shuffled text reading. Our results demonstrate that the zoom lens of attention might be an important concept for eye movement control in reading.
Over the last three decades, the German political economy can be characterized by both institutional continuity and change. Understanding the dynamics of institutional change therefore requires an examination of the interplay of changes in formal institutional rules and how organizations respond to these changes by strategic attempts to promote or hinder further change in institutions. The macro-level political story of institutional change shows a number of paradoxes resulting in unexpected and often incomplete forms of market liberalization shaped by continued support for some core features of Germany's social market economy. The resulting erosion of Germany's co-ordinated model of economic organization through networks and business associations has gone hand-in-hand with the attempts to preserve these institutions for core workers and sectors of the economy in the face of changing environments. The result is a more varied institutional landscape characterized by international diffusion of liberal policies and the politics of their variable re-embedding within a long-term path of institutional continuity.
Using the eye-movement monitoring technique in two reading comprehension experiments, this study investigated the timing of constraints on wh-dependencies (so-called island constraints) in first- and second-language (L1 and L2) sentence processing. The results show that both L1 and L2 speakers of English are sensitive to extraction islands during processing, suggesting that memory storage limitations affect L1 and L2 comprehenders in essentially the same way. Furthermore, these results show that the timing of island effects in L1 compared to L2 sentence comprehension is affected differently by the type of cue (semantic fit versus filled gaps) signaling whether dependency formation is possible at a potential gap site. Even though L1 English speakers showed immediate sensitivity to filled gaps but not to lack of semantic fit, proficient German-speaking learners of English as a L2 showed the opposite sensitivity pattern. This indicates that initial wh-dependency formation in L2 processing is based on semantic feature matching rather than being structurally mediated as in L1 comprehension.
Using the eye-movement monitoring technique in two reading comprehension experiments, this study investigated the timing of constraints on wh-dependencies (so-called island constraints) in first- and second-language (L1 and L2) sentence processing. The results show that both L1 and L2 speakers of English are sensitive to extraction islands during processing, suggesting that memory storage limitations affect L1 and L2 comprehenders in essentially the same way. Furthermore, these results show that the timing of island effects in L1 compared to L2 sentence comprehension is affected differently by the type of cue (semantic fit versus filled gaps) signaling whether dependency formation is possible at a potential gap site. Even though L1 English speakers showed immediate sensitivity to filled gaps but not to lack of semantic fit, proficient German-speaking learners of English as a L2 showed the opposite sensitivity pattern. This indicates that initial wh-dependency formation in L2 processing is based on semantic feature matching rather than being structurally mediated as in L1 comprehension.
This article examines Pierre Nora’s concept of memory using the examples of York and Winchester to demonstrate the individuality of local approaches to the memory of medieval Anglo-Jewries. Overall, this paper will highlight how memory can be rescued from a period of prolonged silence and reintegrated back into a wider historical narrative. Conversely it will also examine how in stark contrast to this new attitude of remembering the silence surrounding Jewish memory continues to exist elsewhere. Finally this paper will ask why this silence remains, and question whether Nora’s theory that memory is constantly evolving is applicable to the experiences of Jewish memory in York and Winchester.