Modulational-instability-free pulse compression in anti-resonant hollow-core photonic crystal fiber

Gas-filled hollow-core photonic crystal fiber (PCF) is used for efficient nonlinear temporal compression of femtosecond laser pulses, two main schemes being direct soliton-effect self-compression, and spectral broadening followed by phase compensation. To obtain stable compressed pulses, it is crucial to avoid decoherence through modulational instability (MI) during spectral broadening. Here we show that changes in dispersion due to spectral anti-crossings between the fundamental core mode and core wall resonances in anti-resonant-guiding hollow-core PCF can strongly alter the MI gain spectrum, enabling MI-free pulse compression for optimized fiber designs. In addition, higher-order dispersion can introduce MI even when the pump pulses lie in the normal dispersion region

Influence of moving breathers on vacancies migration

A vacancy defect is described by a Frenkel--Kontorova model with a discommensuration. This vacancy can migrate when interacts with a moving breather. We establish that the width of the interaction potential must be larger than a threshold value in order that the vacancy can move forward. This value is related to the existence of a breather centred at the particles adjacent to the vacancy.Comment: 11 pages, 10 figure

Experimental evidence for kin-biased helping in a cooperatively breeding vertebrate

The widespread belief that kin selection is necessary for the evolution of cooperative breeding in vertebrates has recently been questioned. These doubts have primarily arisen because of the paucity of unequivocal evidence for kin preferences in cooperative behaviour. Using the cooperative breeding system of long-tailed tits (Aegithalos caudatus) in which kin and non-kin breed within each social unit and helpers are failed breeders, we investigated whether helpers preferentially direct their care towards kin following breeding failure. First, using observational data, we show that not all failed breeders actually become helpers, but that those that do help usually do so at the nest of a close relative. Second, we confirm the importance of kinship for helping in this species by conducting a choice experiment. We show that potential helpers do not become helpers in the absence of close kin and, when given a choice between helping equidistant broods belonging to kin and non-kin within the same social unit, virtually all helped at the nest of kin. This study provides strong evidence that kinship plays an essential role in the maintenance of cooperative breeding in this species

Breathers and kinks in a simulated crystal experiment

We develop a simple 1D model for the scattering of an incoming particle hitting the surface of mica crystal, the transmission of energy through the crystal by a localized mode, and the ejection of atom(s) at the incident or distant face. This is the first attempt to model the experiment described in Russell and Eilbeck in 2007 (EPL, v. 78, 10004). Although very basic, the model shows many interesting features, for example a complicated energy dependent transition between breather modes and a kink mode, and multiple ejections at both incoming and distant surfaces. In addition, the effect of a heavier surface layer is modelled, which can lead to internal reflections of breathers or kinks at the crystal surface.Comment: 15 pages, 12 figures, based on a talk given at the conference "Localized Excitations in Nonlinear Complex Systems (LENCOS)", Sevilla (Spain) July 14-17, 200

Naming the newly found landforms on Venus

The mapping of Venus is unique in the history of cartigraphy; never has so much territory been discovered and mapped in so short a period of time. Therefore, in the interest of international scientific communication, there is a unique urgency to the development of a system of names for surface features on Venus. The process began with the naming of features seen on radar images taken from Earth and continued through mapping expeditions of the U.S. and U.S.S.R. However, the Magellan Mission resolves features twenty-five times smaller than those mapped previously, and its radar data will cover an area nearly equivalent to that of the continents and the sea-floors of the Earth combined. The International Astronomical Union (IAU) was charged with the formal endorsement of names of features on the planets. Proposed names are collected, approved, and applied through the IAU Working Group for Planetary System Nomenclature (WGPSN) and its task groups, prior to IAU approval by the IAU General Assembly. Names approved by the WGPSN and its task groups, prior to final approval may be used on published maps and articles, provided that their provisional nature is stipulated. The IAU has established themes for the names to be used on each of the planets; names of historical and mythological women are used on Venus. Names of political entities and those identified with active religions are not acceptable, and a person must have been deceased for three years or more to be considered. Any interested person may propose a name for consideration by the IAU

Episodic neurologic disorders: syndromes, genes, and mechanisms.

Many neurologic diseases cause discrete episodic impairment in contrast with progressive deterioration. The symptoms of these episodic disorders exhibit striking variety. Herein we review what is known of the phenotypes, genetics, and pathophysiology of episodic neurologic disorders. Of these, most are genetically complex, with unknown or polygenic inheritance. In contrast, a fascinating panoply of episodic disorders exhibit Mendelian inheritance. We classify episodic Mendelian disorders according to the primary neuroanatomical location affected: skeletal muscle, cardiac muscle, neuromuscular junction, peripheral nerve, or central nervous system (CNS). Most known Mendelian mutations alter genes that encode membrane-bound ion channels. These mutations cause ion channel dysfunction, which ultimately leads to altered membrane excitability as manifested by episodic disease. Other Mendelian disease genes encode proteins essential for ion channel trafficking or stability. These observations have cemented the channelopathy paradigm, in which episodic disorders are conceptualized as disorders of ion channels. However, we expand on this paradigm to propose that dysfunction at the synaptic and neuronal circuit levels may underlie some episodic neurologic entities

Alternator and voltage regulator-exciter for a Brayton cycle space power system. Volume 2 - Unbalanced electromagnetic forces

Unbalanced electromagnetic forces in Brayton cycle turboalternator for space power syste

INFLUENCE OF TASTE AND COLOR CUES ON BATHING BY STARLINGS IN APPETITIVE AND ADVERSIVE CONTEXTS: IMPLICATIONS FOR ANIMAL DAMAGE CONTROL

The importance of color and taste in feeding and drinking by omnivorous birds is context·dependent and influenced by learning. Here, we report three experiments designed to assess the influence of such characteristics on starlings. In Experiment 1, eight starlings were given a choice between bathing in red or plain water and 0.15 M NaCI solution or plain water. The frequencies of bathing, drinking, and preening were recorded. Red water was avoided (p \u3c 0.05), but no preferences were observed between NaCI solution and plain water (p \u3e 0.25). That 0.15 M NaCI was not avoided is surprising, because it is rejected by starlings when drinking. Perhaps starlings do not taste substances while bathing but continue to ingest substances that they would otherwise reject. In Experiment 2, we assessed these alternative explanations and also tested (a) whether starlings would bathe in colored water if plain water was unavailable, (b) whether starlings would show preferences among such colors, and (c) whether preferences courd be altered by learning. Twenty-four starlings were assigned to three conditions. Birds in the first condition were presented with red and blue baths and relative preferences for bathing in these colors were assessed. Birds in the second condition were presented with a blue bath and intubated with methiocarb or propylene glycol. Birds in the third condition were presented with a saccharin bath and intubated with methiocarb or propylene glycol. On the four days following treatment, birds in the second condition were given two-choice tests between red and blue baths. Those in the third condition were given two-choice tests between bathing in saccharin solution and plain water. Birds readily bathed in red and blue water when plain water was unavailable. After treatment, however, birds avoided blue water (p \u3c 0.05), but aversions dissipated rapidly. Learned aversions for saccharin were also obtained (p \u3c 0.05); these remained strong over all tests. Experiment 3 was designed to assess the differential importance of taste and color. Sixteen starlings were aSSigned to four groups. Two groups were food-deprived and then given dogfood in a red cup followed by a bath of 0.15 M NaCI or LiCI. The other two groups were presented with a bath of 0.15 M NaCI or LiCI only, as a control. On the four days immediately following treatment, all groups were given two-choice feeding (red vs. blue food cups) and bathing (NaCI vs. plain water) tests. Aversions were expressed towards color in the feeding context (p \u3c 0.05) but not taste in the bathing context (p \u3e 0.25). We inferred that color cues in the feeding context overshadowed taste cues in the bathing context. The present results may have implications for control. Starlings will bathe even under harsh environmental conditions, and one control strategy might be to pair livestock feed with distinctive colors and provide lithium·adulterated bathing stations nearby. Starlings eating feed and bathing in the solution might form color aversions and subsequently avoid the food. Also, the use of such techniques might enhance already existing control, such as the use of starlicide baits. Depredating starlings would be directed toward such baits as birds feeding in the laboratory are directed towards food color combinations not explicitly paired with lithium-induced malaise