The Oort cloud

Views of the large-scale structure of the solar system, consisting of the Sun, the nine planets and their satellites, changed when Oort demonstrated that a gigantic cloud of comets (the Oort cloud) is located on the periphery of the solar system. The following subject areas are covered: (1) the Oort cloud's mass; (2) Hill's cloud mass; (3) angular momentum distribution in the solar system; and (4) the cometary cloud around other stars

How social network heterogeneity facilitates lexical access and lexical prediction

People learn language from their social environment. As individuals differ in their social networks, they might be exposed to input with different lexical distributions, and these might influence their linguistic representations and lexical choices. In this article we test the relation between linguistic performance and 3 social network properties that should influence input variability, namely, network size, network heterogeneity, and network density. In particular, we examine how these social network properties influence lexical prediction, lexical access, and lexical use. To do so, in Study 1, participants predicted how people of different ages would name pictures, and in Study 2 participants named the pictures themselves. In both studies, we examined how participants’ social network properties related to their performance. In Study 3, we ran simulations on norms we collected to see how age variability in one’s network influences the distribution of different names in the input. In all studies, network age heterogeneity influenced performance leading to better prediction, faster response times for difficult-to-name items, and less entropy in input distribution. These results suggest that individual differences in social network properties can influence linguistic behavior. Specifically, they show that having a more heterogeneous network is associated with better performance. These results also show that the same factors influence lexical prediction and lexical production, suggesting the two might be related

Frequency-Domain Coherent Control of Femtosecond Two-Photon Absorption: Intermediate-Field vs. Weak-Field Regime

Coherent control of femtosecond two-photon absorption in the intermediate-field regime is analyzed in detail in the powerful frequency domain using an extended 4th-order perturbative description. The corresponding absorption is coherently induced by the weak-field non-resonant two-photon transitions as well as by four-photon transitions involving three absorbed photons and one emitted photons. The interferences between these two groups of transitions lead to a difference between the intermediate-field and weak-field absorption dynamics. The corresponding interference nature (constructive or destructive) strongly depends on the detuning direction of the pulse spectrum from half the two-photon transition frequency. The model system of the study is atomic sodium, for which both experimental and theoretical results are obtained. The detailed understanding obtained here serves as a basis for coherent control with rationally-shaped femtosecond pulses in a regime of sizable absorption yields.Comment: 25 pages, 5 figure

A superadditivity and submultiplicativity property for cardinalities of sumsets

For finite sets of integers A1, . . . ,An we study the cardinality of the n-fold sumset A1 + · · · + An compared to those of (n − 1)-fold sumsets A1 + · · · + Ai−1 + Ai+1 + · · · + An. We prove a superadditivity and a submultiplicativity property for these quantities. We also examine the case when the addition of elements is restricted to an addition graph between the sets

A blade for all seasons? Making and using Amudian blades at Qesem Cave, Israel

The Qesem Cave prehistoric sequence consists of one dominant lithic industry - the Amudian, a part of the Acheulo-Yabrudian (late Lower Paleolithic) cultural complex. The Acheulo-Yabrudian complex comprises three major lithic industries - Acheulo-Yabrudian, Yabrudian and Pre-Aurignacian/Amudian. While the first two industries are dominated by typical Lower Paleolithic lithic traditions, namely flake production technologies, hand-axes and scrapers, the Amudian presents an innovative blade industry. This relatively poorly known industry is of importance being stratigraphically situated between the Lower Paleolithic Acheulian and the Middle Paleolithic Mousterian. The available radiometric dates for this entity indicate a range from ca. 400 to about 200 kyr. The Amudian in the Levant is characterized by systematic blade production and a major component of shaped blades. At Qesem Cave the majority of the lithic artefacts belong to the Amudian industry with distinctive blade-dominated assemblages throughout a stratigraphic sequence of 7.5 meters. During the 2006 excavation season a scraper-dominated Yabrudian assemblage was discovered, indicating variability and more complex human behaviour at the cave rather than specialized blade-related activities only. The Amudian at Qesem Cave is a very early blade production industry and it reflects technological choices of the artisans as well as specific modes of resource exploitation and subsistence activities. This paper will summarize the current state of research on the Qesem cave lithic assemblages, focusing on the composition of the rich Amudian assemblages, the reconstruction of Amudian blade production and the functional interpretation of Amudian blades. A short survey of the new Yabrudian assemblage will be provided as well. We finally discuss interpretations of Acheulo-Yabrudian lithic variability and the meaning of late Lower Paleolithic blade production as a technological, functional and cultural phenomenon.The Qesem Cave prehistoric sequence consists of one dominant lithic industry - the Amudian, a part of the Acheulo-Yabrudian (late Lower Paleolithic) cultural complex. The Acheulo-Yabrudian complex comprises three major lithic industries - Acheulo-Yabrudian, Yabrudian and Pre-Aurignacian/Amudian. While the first two industries are dominated by typical Lower Paleolithic lithic traditions, namely flake production technologies, hand-axes and scrapers, the Amudian presents an innovative blade industry. This relatively poorly known industry is of importance being stratigraphically situated between the Lower Paleolithic Acheulian and the Middle Paleolithic Mousterian. The available radiometric dates for this entity indicate a range from ca. 400 to about 200 kyr. The Amudian in the Levant is characterized by systematic blade production and a major component of shaped blades. At Qesem Cave the majority of the lithic artefacts belong to the Amudian industry with distinctive blade-dominated assemblages throughout a stratigraphic sequence of 7.5 meters. During the 2006 excavation season a scraper-dominated Yabrudian assemblage was discovered, indicating variability and more complex human behaviour at the cave rather than specialized blade-related activities only. The Amudian at Qesem Cave is a very early blade production industry and it reflects technological choices of the artisans as well as specific modes of resource exploitation and subsistence activities