The enigmatic mineral particle accumulations on the cuticular rings of marine desmoscolecoid nematodes structure and significance explained with clues from live observations

The majority of Desmoscolecoidea are characterized by ring-shaped accumulations of mineral particles on the cuticle resulting in the impression of a peculiar body articulation. Live observations made during the extraction of desmoscolecoids from mud sampled in the Swedish Gullmar fjord suggested new ideas pertinent to the particle accretion and the likely functional significance of the prominent rings. Undisturbed desmoscolecoids were observed to perform perpetual, vigorous, stationary undulations with their body. In our opinion these undulations affect the distribution of particles adhering to the cuticle by pushing them from soft, pliable cuticular sections to comparably stiff rings thus generating distinct concretion rings and naked interzones. The prominent concretion rings are assumed to increase positive mechanical effects of the undulations on the productivity of ubiquitous microbial populations residing on ambient sediment particles. The microbial production boosted by this kind of bioturbation may be of nutritional importance for the desmoscolecoids. An electron-microscopic investigation (TEM) of Tricoma sp. from the Gullmar fjord revealed the concretion rings to consist of stacks of clay mineral platelets in the submicrometer size range. A perusal through contributions of other authors suggests that such clay mineral aggregates are the basic component (granular component sensu Timm 1970) in the concretion rings of all desmoscolecoids. In a number of species these aggregates contain a specifically determined admixture ofconspicuous other mineral grains

Inhomogeneous Fixed Point Ensembles Revisited

The density of states of disordered systems in the Wigner-Dyson classes approaches some finite non-zero value at the mobility edge, whereas the density of states in systems of the chiral and Bogolubov-de Gennes classes shows a divergent or vanishing behavior in the band centre. Such types of behavior were classified as homogeneous and inhomogeneous fixed point ensembles within a real-space renormalization group approach. For the latter ensembles the scaling law $\mu=d\nu-1$ was derived for the power laws of the density of states $\rho\propto|E|^\mu$ and of the localization length $\xi\propto|E|^{-\nu}$. This prediction from 1976 is checked against explicit results obtained meanwhile.Comment: Submitted to 'World Scientific' for the volume 'Fifty Years of Anderson Localization'. 12 page

Evaluating the summer night sky brightness at a research field site on Lake Stechlin in northeastern Germany

We report on luminance measurements of the summer night sky at a field site on a freshwater lake in northeastern Germany (Lake Stechlin) to evaluate the amount of artificial skyglow from nearby and distant towns in the context of a planned study on light pollution. The site is located about 70 km north of Berlin in a rural area possibly belonging to one of the darkest regions in Germany. Continuous monitoring of the zenith sky luminance between June and September 2015 was conducted utilizing a Sky Quality Meter. With this device, typical values for clear nights in the range of 21.5-21.7 mag$_{SQM}/$arcsec$^2$ were measured, which is on the order of the natural sky brightness during starry nights. On overcast nights, values down to 22.84 mag$_{SQM}/$arcsec$^2$ were obtained, which is about one third as bright as on clear nights. The luminance measured on clear nights as well as the darkening with the presence of clouds indicate that there is very little influence of artificial skyglow on the zenith sky brightness at this location. Furthermore, fish-eye lens sky imaging luminance photometry was performed with a digital single-lens reflex camera on a clear night in the absence of moonlight. The photographs unravel several distant towns as possible sources of light pollution on the horizon. However, the low level of artificial skyglow makes the field site at Lake Stechlin an excellent location to study the effects of skyglow on a lake ecosystem in a controlled fashion.Comment: 20 pages, 8 figures, Journal of Quantitative Spectroscopy and Radiative Transfer 201

The effects of rigid polyurethane foam as a confinement material on breaching charge detonations

The effects of a rigid polyurethane foam used as a confinement material on four types of breaching explosives were tested, focusing on the changes in shockwave peak pressures, detonation load compression forces, and brisance cratering abilities. The Plate Dent testing procedure was modified to incorporate a load cell force sensor, and two air overpressure sensors were included adjacent to the blast to quantify each test result. The testing variables focused on the polyurethane foam cure times and thickness volumes around the breaching explosives to determine the breaching charges\u27 optimal energy output capabilities when confined by the foam material. The rigid foam confinement increased the compression forces and brisance cratering abilities of all four tested explosives types as the foam cure times were extended and foam confinement radius increased. A reduction in the positive peak blast pressure was noted as the foam confinement material was increased. An increase in the peak blast pressure and compression force occurred when the polyurethane foam cure times were extended. When confined by the polyurethane foam, the average compression force was increased by 483% and the average Plate Dent depths were increased by 26.4%. The average blast peak pressure of a polyurethane foam confined detonation was 10% less than an unconfined detonation. This study\u27s findings show how a breaching charge confined by polyurethane foam would provide a more damaging blast force to a structure while reducing the blast exposure to the breaching team performing the explosive breach --Abstract, page iii

Vibratory behavior of the sound generating structures of the bird syrinx

Journal ArticleRecent endoscopic studies of the bird syrinx during phonation suggest that sound is generated by vibrating membrane folds or labia (Goller and Larsen, J. exp. Biol., 200, 2165-2176, 1997; Goller and Larsen, Proc. Natl. Acad. Sci., 4,14787-14791, 1997) and not by a whistle mechanism (Nottebohm, J. comp. Physiol., 108, 157-170, 1976; Gaunt et a!., Auk, 99, 474-494, 1982)

Digraphs, Knowledge Hypernets, and Neurons

A current flow network of switches, with input node I and output node O, are represented by a directed graph G. In G we define a model of a neuron, and introduce another model in which neurons are theoretically linked. In this second model, we cover invariance, information flow and noise. We show how this model arises from G, how it can be taught, and how it can be declaratively interpreted. The system is made dynamic due to the closing, from O to I, through the environment of the combined models, of a feedback circuit