Density of states in random lattices with translational invariance

We propose a random matrix approach to describe vibrational excitations in disordered systems. The dynamical matrix M is taken in the form M=AA^T where A is some real (not generally symmetric) random matrix. It guaranties that M is a positive definite matrix which is necessary for mechanical stability of the system. We built matrix A on a simple cubic lattice with translational invariance and interaction between nearest neighbors. We found that for certain type of disorder phonons cannot propagate through the lattice and the density of states g(w) is a constant at small w. The reason is a breakdown of affine assumptions and inapplicability of the elasticity theory. Young modulus goes to zero in the thermodynamic limit. It strongly reminds of the properties of a granular matter at the jamming transition point. Most of the vibrations are delocalized and similar to diffusons introduced by Allen, Feldman et al., Phil. Mag. B v.79, 1715 (1999).Comment: 4 pages, 5 figure

On Design Education

As Heape (2015) reminds us, today’s students are tomorrow’s practitioners (and researchers we add). For Design this poses a number of important educational challenges and possibilities. From an Indian context, Majithia (2017) sees a need to transform the role of the designer and the preparation of young professionals for futures that are volatile and ambiguous. These are some of the issues we take up in this book and especially in this essay in which we reconsider the legacies, practices, pedagogies and prospects of design education

Helophorus Fabricius 1775

<i>Helophorus</i> Fabricius, 1775 <p> <b>Type species.</b> <i>Silpha aquatica</i> Linnaeus, 1758 (= <i>Helophorus</i> (s. str.) <i>aquaticus</i> (Linnaeus, 1758) (modern)), designated by LATREILLE (1810).</p> <p> <b>Time range.</b> Late Jurassic (ca. 150–146 mya) to recent.</p> <p> <b> Diagnosis. <i>Adult</i>:</b> Head and pronotum at least partly with setiferous granules in most species (granulation totally reduced in few species only); frontoclypeal suture very distinct, its median portion grooved; mentum distinctly transverse or only slightly wider than long; gula usually strongly constricted (moderately wide with well-separated gular sutures in few species only); pronotum with one to five longitudinal grooves (if less than five grooves are present, then all pronotal intervals bear large and very distinct setiferous granules); lateral margin of pronotum at least slightly crenulate; anterolateral portion of hypomeron with antennal groove; mesanepisterna not meeting mesally; mesoventrite very narrow at anterior margin, bearing a transverse ridge posteromedially; elytra of variable coloration, but never pale with dark stripes along elytral series; elytra in some species with elevated or costate alternate intervals.</p> <p> <b> <i>Larva</i>:</b> Head prognathous; nasale simply triangular or with lobate lateral margins; epistomal lobes large, slightly overlapping nasale, bearing series of stout setae; mandible with two retinacular teeth; labium without ligula; each parietale with 6 stemmata situated in area of darker cuticle; all thoracic segments with large dorsal tergite; abdominal segments 1–8 each with a pair of dorsal sclerites and an additional large sclerite laterally of them on each side; tracheal system holopneustic, spiracular atrium absent; urogomphi large, three-segmented.</p>Published as part of <i>Fikáček, Martin, Prokin, Alexander, Angus, Robert B., Pono, Alexander, Marenko, Yue, Yanli, Ren, Dong & Prokop, Jakub, 2012, Revision of Mesozoic fossils of the helophorid lineage of the superfamily Hydrophiloidea (Coleoptera: Polyphaga), pp. 89-127 in Acta Entomologica Musei Nationalis Pragae 52 (1)</i> on page 103, DOI: <a href="http://zenodo.org/record/5330604">10.5281/zenodo.5330604</a&gt

Revision of Mesozoic fossils of the helophorid lineage of the superfamily Hydrophiloidea (Coleoptera: Polyphaga)

Fikáček, Martin, Prokin, Alexander, Angus, Robert B., Pono, Alexander, Marenko, Yue, Yanli, Ren, Dong, Prokop, Jakub (2012): Revision of Mesozoic fossils of the helophorid lineage of the superfamily Hydrophiloidea (Coleoptera: Polyphaga). Acta Entomologica Musei Nationalis Pragae 52 (1): 89-127, DOI: http://doi.org/10.5281/zenodo.533060

Mesohelophorus Ponomarenko 1977

Subgenus † Mesohelophorus Ponomarenko, 1977 stat. nov. Mesohelophorus Ponomarenko, 1977b: 113. Type species. Mesohelophorus sibiricus Ponomarenko, 1977 (= H. palaeosibiricus nom. nov.) (by original designation). Time range. Early Cretaceous, Berriasian – Hauterivian, ca. 146–135 mya. Diagnosis. Adult: Body rather wide; mentum ca. as wide as long; gula constricted, gular sutures joint at a point; maxillary palpomere 4 symmetrical; pronotum with three longitudinal furrows; pronotal intervals bearing very distinct granulation; pronotal flanks narrow; elytron with rather long scutellar stria; alternate elytral intervals not elevated or costate; epipleuron well-developed, wide anteriorly. By the rather wide body, strongly granulate pronotum, constricted gula and symmetrical maxillary palpomere 4, Mesohelophorus resembles the species of the modern subgenera Empleurus Hope, 1838, Transithelophorus Angus, 1970, Eutrichelophorus Sharp, 1915 and Kyphohelophorus Kuwert, 1886. It may be easily distinguished from them by the presence of only three pronotal furrows (five in the modern subgenera), elytra without elevated alternate intervals or tubercles (elevated in Empleurus, Transithelophorus and Eutrichelophorus, bearing tubercles in Kyphohelophorus) and wide elytral epipleura (extremely narrow in modern taxa). In addition, it differs from Empleurus by narrow pronotal flanks (very wide in Empleurus). Mesohelophorus also resembles the modern H. (Orphelophorus) arcticus Brown, 1937 by the reduced number of pronotal grooves and strong pronotal granulation, but may be easily distinguished from it by the rather long scutellar stria on the elytron (the scutellary stria is absent, or very rarely consists of one or two punctures only in H. arcticus). Taxonomic note. Due to the presence of all diagnostic characters of Helophorus, we downgrade Mesohelophorus to a subgenus of Helophorus which seems to be confined to the early Cretaceous only. Three species of Mesohelophorus have been described till now, of which only M. palaeosibiricus nom. nov. belongs to the subgenus. Mesohelophorus elongatus is synonymised with Helophorus (Mesosperchus) tarsalis above, and Mesohelophorus mongolicus Ponomarenko, 1986 is transferred to the Buprestoidea below.Published as part of Fikáček, Martin, Prokin, Alexander, Angus, Robert B., Pono, Alexander, Marenko, Yue, Yanli, Ren, Dong & Prokop, Jakub, 2012, Revision of Mesozoic fossils of the helophorid lineage of the superfamily Hydrophiloidea (Coleoptera: Polyphaga), pp. 89-127 in Acta Entomologica Musei Nationalis Pragae 52 (1) on page 109, DOI: 10.5281/zenodo.533060