Non-linear generation of acoustic noise in the IAR spacecraft

The requirement to produce high level acoustic noise fields with increasing accuracy in environmental test facilities dictates that a more precise understanding is required of the factors controlling nonlinear noise generation. Details are given of various nonlinear effects found in acoustic performance data taken from the IAR Spacecraft Acoustic Chamber. This type of data has enabled the IAR to test large spacecraft to relatively tight acoustic tolerances over a wide frequency range using manually set controls. An analog random noise automatic control system was available and modified to provide automatic selection of the chamber's spectral sound pressure levels. The automatic control system when used to complete a typical qualification test appeared to equal the accuracy of the manual system and had the added advantage that parallel spectra could be easily achieved during preset tests

Phospholipides containing amino acids other than serine. I. Detection

In view of the widespread occurrence of the amino acid-containing lipides and the unique course of their metabolism during development of Drosophila, we have carried out extensive investigations concerned with their isolation and chemical nature. The present report is concerned primarily with techniques and procedures developed to insure removal of non-lipide contaminants from preparations of these lipides

Big Data in Maritime Archaeology: Challenges and Prospects from the Middle East and North Africa

The Middle East and North Africa have witnessed a surfeit of geospatial data collection projects, resulting in big databases with powerful deductive capacities. Despite the valuable insights and expansive evidentiary record offered by those databases, emphasis on anthropogenic threats to cultural heritage, combined with a limited integration of local perspectives, have raised important questions on the ethical and epistemological dimensions of big data. This paper contextualizes maritime cultural heritage (MCH) in those debates through the lens of the Maritime Endangered Archaeology in the Middle East and North Africa project (MarEA). MarEA is developing a unique for the region database for MCH designed to amalgamate a baseline record emphasizing spatial location, state of preservation, and vulnerability. This record will form a stepping stone toward finer-grained research on MCH and its interdisciplinary intersections. It is also developed as an information resource to facilitate local collaborators in prioritizing site monitoring and developing documentation, management, and mitigation strategies.</p

Cold gas as an ice diagnostic toward low mass protostars

Up to 90% of the chemical reactions during star formation occurs on ice surfaces, probably including the formation of complex organics. Only the most abundant ice species are however observed directly by infrared spectroscopy. This study aims to develop an indirect observational method of ices based on non-thermal ice desorption in the colder part of protostellar envelopes. For that purpose the IRAM 30m telescope was employed to observe two molecules that can be detected both in the gas and the ice, CH3 OH and HNCO, toward 4 low mass embedded protostars. Their respective gas-phase column densities are determined using rotational diagrams. The relationship between ice and gas phase abundances is subsequently determined. The observed gas and ice abundances span several orders of magnitude. Most of the CH3OH and HNCO gas along the lines of sight is inferred to be quiescent from the measured line widths and the derived excitation temperatures, and hence not affected by thermal desorption close to the protostar or in outflow shocks. The measured gas to ice ratio of ~10-4 agrees well with model predictions for non-thermal desorption under cold envelope conditions and there is a tentative correlation between ice and gas phase abundances. This indicates that non-thermal desorption products can serve as a signature of the ice composition. A larger sample is however necessary to provide a conclusive proof of concept.Comment: accepted by A&A letters, 10 pages including 5 figure

Big Data in Maritime Archaeology: Challenges and Prospects from the Middle East and North Africa

The Middle East and North Africa have witnessed a surfeit of geospatial data collection projects, resulting in big databases with powerful deductive capacities. Despite the valuable insights and expansive evidentiary record offered by those databases, emphasis on anthropogenic threats to cultural heritage, combined with a limited integration of local perspectives, have raised important questions on the ethical and epistemological dimensions of big data. This paper contextualizes maritime cultural heritage (MCH) in those debates through the lens of the Maritime Endangered Archaeology in the Middle East and North Africa project (MarEA). MarEA is developing a unique for the region database for MCH designed to amalgamate a baseline record emphasizing spatial location, state of preservation, and vulnerability. This record will form a stepping stone toward finer-grained research on MCH and its interdisciplinary intersections. It is also developed as an information resource to facilitate local collaborators in prioritizing site monitoring and developing documentation, management, and mitigation strategies

Behavioural plasticity and the transition to order in jackdaw flocks

This is the final version. Available on open access from Nature Research via the DOI in this recordData availability: Raw images captured by one of the four cameras and the reconstructed 3D movement trajectories of the jackdaws are provided in Supplementary Movies 1 to 3. The group density and group order for 154 groups are provided in Supplementary Data 1. Plain text files, each including bird ID number, position, time, and velocity at every time step are provided in Supplementary Data 2 to 4. All data required to reproduce the results in this study are included in Supplementary Data 1 to 4. The data analysis codes (including the self-propelled particle model) to generate all figures in the paper are also provided. Supplementary Data, Supplementary Movies, and data analysis codes are available at: https://figshare.com/s/472d354cc9e823a8f48fCollective behaviour is typically thought to arise from individuals following fixed interaction rules. The possibility that interaction rules may change under different circumstances has thus only rarely been investigated. Here we show that local interactions in flocks of wild jackdaws (Corvus monedula) vary drastically in different contexts, leading to distinct group-level properties. Jackdaws interact with a fixed number of neighbours (topological interactions) when traveling to roosts, but coordinate with neighbours based on spatial distance (metric interactions) during collective anti-predator mobbing events. Consequently, mobbing flocks exhibit a dramatic transition from disordered aggregations to ordered motion as group density increases, unlike transit flocks where order is independent of density. The relationship between group density and group order during this transition agrees well with a generic self-propelled particle model. Our results demonstrate plasticity in local interaction rules and have implications for both natural and artificial collective systems.Human Frontier Science Progra