Extraordinary cranial specialization in a new genus of extinct duck (Aves: Anseriformes) from Kauai, Hawaiian Islands

Zootaxa ◽  
2009 ◽  
Vol 2296 (1) ◽  
pp. 47-67 ◽  
Author(s):  
ANDREW N. IWANIUK ◽  
STORRS L. OLSON ◽  
HELEN F. JAMES
Keyword(s):  
New Genus ◽  
Hawaiian Islands ◽  
Foramen Magnum ◽  
Exit Point ◽  
Cross Sectional ◽  
Mandibular Foramen ◽  
Extant Species ◽  
Order Of Magnitude ◽  
Living Species ◽  
Tactile Cues

Talpanas lippa is described as a new genus and species of waterfowl from Kauai, Hawaiian Islands, that is unlike any other known member of the order. It is characterized by a short, stout tarsometatarsus and a braincase that is shallow and wide relative to its length with very small orbits. In comparison with extant species, the optic foramen of Talpanas is remarkably small whereas the maxillo-mandibular foramen, which is the exit point of the trigeminal nerve, is grossly enlarged. Relative to skull length and foramen magnum area, the maxillo-mandibular foramen is one order of magnitude larger in cross-sectional area than that of extant Anseriformes. We conclude that Talpanas had reduced visual abilities, as reflected externally by its small orbits and optic foramen, and a grossly hypertrophied trigeminal foramen. Taken together, this suggests that Talpanas may have been more heavily reliant upon somatosensory (tactile) cues for foraging than any living species of bird. Pectoral elements are unknown, but the evident lack of keen eyesight suggests that the species was flightless, as were many other insular waterfowl.

Diagnostics of metal samples using the results of experimental and theoretical study of positively charged microparticles formed upon sample destruction

2018 ◽  
Vol 84 (10) ◽  
pp. 23-28
Author(s):  
D. A. Golentsov ◽  
A. G. Gulin ◽  
Vladimir A. Likhter ◽  
K. E. Ulybyshev
Keyword(s):  
Experimental Data ◽  
Early Stage ◽  
Experimental Studies ◽  
Material Model ◽  
Total Charge ◽  
Cross Sectional ◽  
Practical Applications ◽  
Mechanical And Electrical Properties ◽  
Order Of Magnitude ◽  
Using Data

Destruction of bodies is accompanied by formation of both large and microscopic fragments. Numerous experiments on the rupture of different samples show that those fragments carry a positive electric charge. his phenomenon is of interest from the viewpoint of its potential application to contactless diagnostics of the early stage of destruction of the elements in various technical devices. However, the lack of understanding the nature of this phenomenon restricts the possibility of its practical applications. Experimental studies were carried out using an apparatus that allowed direct measurements of the total charge of the microparticles formed upon sample rupture and determination of their size and quantity. The results of rupture tests of duralumin and electrical steel showed that the size of microparticles is several tens of microns, the particle charge per particle is on the order of 10–14 C, and their amount can be estimated as the ratio of the cross-sectional area of the sample at the point of discontinuity to the square of the microparticle size. A model of charge formation on the microparticles is developed proceeding from the experimental data and current concept of the electron gas in metals. The model makes it possible to determine the charge of the microparticle using data on the particle size and mechanical and electrical properties of the material. Model estimates of the total charge of particles show order-of-magnitude agreement with the experimental data.

Numerical Prediction of Flow and Heat Transfer in a Parallel Plate Channel With Staggered Fins

1987 ◽  
Vol 109 (1) ◽  
pp. 25-30 ◽  
Author(s):  
K. M. Kelkar ◽  
S. V. Patankar
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Periodic Variation ◽  
Local Heat ◽  
Temperature Fields ◽  
Parallel Plates ◽  
Constant Property ◽  
Cross Sectional ◽  
Flow And Heat Transfer ◽  
Order Of Magnitude

Fluid flow and heat transfer in two-dimensional finned passages were analyzed for constant property laminar flow. The passage is formed by two parallel plates to which fins are attached in a staggered fashion. Both the plates are maintained at a constant temperature. Streamwise periodic variation of the cross-sectional area causes the flow and temperature fields to repeat periodically after a certain developing length. Computations were performed for different values of the Reynolds number, the Prandtl number, geometric parameters, and the fin-conductance parameter. The fins were found to cause the flow to deflect significantly and impinge upon the opposite wall so as to increase the heat transfer significantly. However, the associated increase in pressure drop was an order of magnitude higher than the increase in heat transfer. Streamline patterns and local heat transfer results are presented in addition to the overall results.

The stress generated in a non-dilute suspension of elongated particles by pure straining motion

1971 ◽  
Vol 46 (4) ◽  
pp. 813-829 ◽  
Author(s):  
G. K. Batchelor
Keyword(s):  
Theoretical Formula ◽  
Rigid Sphere ◽  
Cross Sectional ◽  
Outer Flow ◽  
Rigid Particles ◽  
Bulk Stress ◽  
Order Of Magnitude ◽  
Sectional Plane ◽  
Dilute Suspension ◽  
A Minor

In a pure straining motion, elongated rigid particles in suspension are aligned parallel to the direction of the greatest principal rate of extension, provided the effect of Brownian motion is weak. If the suspension is dilute, in the sense that the particles are hydrodynamically independent, each particle of length 2l makes a contribution to the bulk deviatoric stress which is of roughly the same order of magnitude as that due to a rigid sphere of radius l. The fractional increase in the bulk stress due to the presence of the particles is thus equal to the concentration by volume multiplied by a factor of order l2/b2, where 2b is a measure of the linear dimensions of the particle cross-section. This suggests that the stress due to the particles might be relatively large, for volume fractions which are still small, with interesting implications for the behaviour of polymer solutions. However, dilute-suspension theory is not applicable in these circumstances, and so an investigation is made of the effect of interactions between particles. It is assumed that, when the average lateral spacing of particles (h) satisfies the conditions b [Lt ] h [Lt ] l, the disturbance velocity vector is parallel to the particles and varies only in the cross-sectional plane. The velocity near a particle is found to have the same functional form as for an isolated particle, and the modification to the outer flow field for one particle is determined by replacing the randomly placed neighbouring particles by an equivalent cylindrical boundary. The resulting expression for the contribution to the bulk stress due to the particles differs from that for a dilute suspension only in a minor way, viz. by the replacement of log 2l/b by log h/b, and the above suggestion is confirmed. The relative error in the expression for the stress is expected to be of order (log h/b)−1. Some recent observations by Weinberger of the stress in a suspension of glass-fibre particles for which 2l/h = 7·4 and h/2b = 7·8 do show a particle stress which is much larger than the ambient-fluid stress, although the theoretical formula is not accurate under these conditions.

scholarly journals Effect of Post-Process Curing and Washing Time on Mechanical Properties of mSLA Printouts

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4856
Author(s):  
Bartłomiej Nowacki ◽  
Paweł Kowol ◽  
Mateusz Kozioł ◽  
Piotr Olesik ◽  
Jakub Wieczorek ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Curing Time ◽  
Cross Sectional ◽  
Post Process ◽  
Order Of Magnitude ◽  
Static Tensile ◽  
High Roughness ◽  
Ambiguous Effect

The article discusses the influence of the post-process on the mechanical properties of elements produced with the use of the mask stereolithography (mSLA) method. Printed samples were subjected to the following post-process steps: Washing and post-curing, at various times. Then, static tensile and static bending tests were carried out, as well as Shore D hardness measurements for the inner and surface part of the sample, as well as profilographometric analysis of the surface. The post-curing time has been found to strongly affect the tensile and bending strength of printouts, and to improve their surface quality. Washing has an ambiguous effect on the strength of the printouts, but, in the end, it was found that extended washing slightly reduces the strength. Washing significantly affects the quality of the printout surface. A washing time that is too short results in a surface that strongly resembles the printing process, with high roughness. Increasing the washing time to 10 min lowers the roughness by one order of magnitude. Post-curing has also been shown to be beneficial for the cured sample with the application of shielding water. This approach results in an improvement in the flexural strength of the printouts. In general, the obtained research results indicate that, for printouts with cross-sectional dimensions of several mm, the optimal washing time is no more than 10 min and the post-curing time is at least 30 min.

scholarly journals A Second Endemic Land Mammal for the Hawaiian Islands: A New Genus and Species of Fossil Bat (Chiroptera: Vespertilionidae)

2016 ◽  
Vol 3854 (3854) ◽  
pp. 1-52 ◽  
Author(s):  
Alan C. Ziegler ◽  
Francis G. Howarth ◽  
Nancy B. Simmons
Keyword(s):  
New Genus ◽  
Hawaiian Islands ◽  
New Genus And Species ◽  
Land Mammal

Deep Level Defect Studies in Mocvd-Grown InxGa1−sAs1−yNy Films Lattice-Matched to GaAs

1998 ◽  
Vol 535 ◽  
Author(s):  
Daewon Kwon ◽  
R. J. Kaplar ◽  
J. J. Boeckl ◽  
S. A. Ringel ◽  
A. A. Allerman ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Deep Level ◽  
Energy Levels ◽  
Resolution Limit ◽  
Defect States ◽  
Cross Sectional ◽  
Order Of Magnitude ◽  
Transient Spectroscopy ◽  
Lattice Matched ◽  
Dlts Spectra

AbstractDeep level defects in MOCVD-grown, unintentionally doped p-type InGaAsN films lattice matched to GaAs were investigated using deep level transient spectroscopy (DLTS) measurements. As-grown p-InGaAsN showed broad DLTS spectra suggesting that there exists a broad distribution of defect states within the band-gap. Moreover, the trap densities exceeded 1015 cm−3. Cross sectional transmission electron microscopy (TEM) measurements showed no evidence for threading dislocations within the TEM resolution limit of 107 cm−2. A set of samples was annealed after growth for 1800 seconds at 650 °C to investigate the thermal stability of the traps. The DLTS spectra of the annealed samples simplified considerably, revealing three distinct hole trap levels with energy levels of 0.10 eV, 0.23 eV, and 0.48 eV above the valence band edge with trap concentrations of 3.5 × 1014 cm−3, 3.8 × 1014 cm−3, and 8.2 × 1014 cm−3, respectively. Comparison of as-grown and annealed DLTS spectra showed that post-growth annealing effectively reduced the total trap concentration by an order of magnitude across the bandgap. However, the concentration of a trap with an energy level of 0.48 eV was not affected by annealing indicating a higher thermal stability for this trap as compared with the overall distribution of shallow and deep traps.

Orsonwelles, a new genus of giant linyphiid spiders (Araneae) from the Hawaiian Islands

2002 ◽  
Vol 16 (3) ◽  
pp. 369 ◽  
Author(s):  
G. Hormiga
Keyword(s):  
Type Species ◽  
New Genus ◽  
Hawaiian Islands ◽  
Morphological Characters ◽  
Hawaiian Archipelago ◽  
Web Architecture ◽  
Island Endemics ◽  
Close Relatives

The Hawaiian spider genus Orsonwelles, gen. nov. (Araneae : Linyphiidae) is described. All Orsonwelles species are single island endemics: Kauai harbours six species; Oahu has three; Molokai has two; and Maui and Hawaii have one species each. The thirteen species included in Orsonwelles are described and illustrated: O. torosus (Simon), comb. nov., O. malus, sp. nov., O. calx, sp. nov., O. ventus, sp. nov., O. bellum, sp. nov. and O. iudicium, sp. nov. from Kauai; O. polites, sp. nov. (the type species), O. ambersonorum, sp. nov. and O. arcanus, sp. nov. from Oahu; O. othello, sp. nov. and O. macbeth, sp. nov. from Molokai; O. falstaffius, sp. nov. from Maui; and O. graphicus (Simon), comb. nov. from Hawaii. A total of 55 morphological characters (plus one behavioural character) were scored for twelve taxa (four Orsonwelles species plus eight linyphiid outgroups) to test the monophyly of the genus using cladistic methods. The most parsimonious cladograms provide robust character support for the monophyly of Orsonwelles. A single colonisation of the Hawaiian archipelago is hypothesised to explain the presence of these species in the Hawaiian Islands. This genus represents a case of insular gigantism (these are the largest linyphiids described), although the close relatives of Orsonwelles remain unknown. Their web architecture is also described and illustrated.

Allonautilus: a new genus of living nautiloid cephalopod and its bearing on phylogeny of the Nautilida

1997 ◽  
Vol 71 (6) ◽  
pp. 1054-1064 ◽  
Author(s):  
Peter D. Ward ◽  
W. Bruce Saunders
Keyword(s):  
Phylogenetic Analysis ◽  
Reproductive System ◽  
New Genus ◽  
Male Reproductive System ◽  
Late Cenozoic ◽  
Extant Species ◽  
Single Genus ◽  
Gill Morphology ◽  
First Time

Living ectocochliate cephalopods have long been thought to be restricted to a single genus, Nautilus Linnaeus, 1758, comprising five or six extant species. The shells of two species, N. scrobiculatus Lightfoot, 1786, and N. perforatus Conrad, 1847, are quite distinct, but no soft-parts were known until 1984, when N. scrobiculatus was seen alive for the first time. Dissections show that significant anatomical differences exist between N. scrobiculatus and other Nautilus species, including differences in gill morphology and details of the male reproductive system. These differences, along with phylogenetic analysis of extant and selected fossil nautiloid species, indicate that N. scrobiculatus, and N. perforatus should be distinguished from Nautilus as a newly defined genus, Allonautilus. This analysis contradicts previous phylogenies proposed for the Nautilida, which placed Nautilus as the last-evolved member of the order. We surmise that Allonautilus is a descendent of Nautilus, that the latter is paraphyletic, and first evolved in the Mesozoic, rather than in the late Cenozoic, as has been previously suggested.

An investigation on the permeability of different wood furnish materials

Holzforschung ◽  
2008 ◽  
Vol 62 (2) ◽  
pp. 215-222 ◽  
Author(s):  
Heiko Thoemen ◽  
André Klueppel
Keyword(s):  
Hot Pressing ◽  
Gas Permeability ◽  
Core Layer ◽  
Raw Material ◽  
Cross Sectional ◽  
Wood Particles ◽  
Order Of Magnitude ◽  
Lower Permeability ◽  
Size Of Particles ◽  
Wood Based Composite

Abstract In wood-based composite mats, mass and heat transfer are substantially influenced by their gas permeability. Thus, reliable permeability data are needed if one wants to model and simulate those processes taking place prior, during, and after hot-pressing operations of the mat. In this study, wood particles of surface and core layer type were obtained from two particleboard manufacturers, using impact mills and knife ring flakers, respectively. The permeability measurements were performed on the initial materials, as well as on subsets of it obtained by laboratory sieving. Additionally, medium density fibreboard (MDF) fibres from three species, namely pine (Pinus sylvestris), spruce (Picea abies) and rubberwood (Hevea Brasiliensis) were investigated. Cross-sectional and within-plane permeability was measured for densities from 250 to 1000 kg m-3. The permeability of the core particle materials was determined on solidified samples. On the other hand, the surface particles and MDF fibres were investigated by means of a rapid testing method on loose furnish materials (without solidification). MDF mats exhibited lower permeability values than particle mats at low densities, but values were found in the same order of magnitude for high densities. Mainly, the small particles determine the pore structure and permeability of particle mats. Thickness and in-plane size of particles affect the mat permeability, with the in-plane size becoming primarily effective at elevated densities. The permeability of MDF fibre mats depends more on the anatomy of the raw material than on its size distribution. We suggest, based on computer simulations, that only the within-plane permeability has a strong effect on gas pressure and temperature conditions during hot pressing. The cross-sectional permeability does not play an essential role in this regard.

scholarly journals Force per cross-sectional area from molecules to muscles: a general property of biological motors

2016 ◽  
Vol 3 (7) ◽  
pp. 160313 ◽  
Author(s):  
Jean-Pierre Rospars ◽  
Nicole Meyer-Vernet
Keyword(s):  
Molecular Motors ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Specific Tension ◽  
Order Of Magnitude ◽  
Taxonomic Groups ◽  
Large Animals ◽  
Basic Order ◽  
Biological Motors

We propose to formally extend the notion of specific tension, i.e. force per cross-sectional area—classically used for muscles, to quantify forces in molecular motors exerting various biological functions. In doing so, we review and compare the maximum tensions exerted by about 265 biological motors operated by about 150 species of different taxonomic groups. The motors considered range from single molecules and motile appendages of microorganisms to whole muscles of large animals. We show that specific tensions exerted by molecular and non-molecular motors follow similar statistical distributions, with in particular, similar medians and (logarithmic) means. Over the 10 19 mass ( M ) range of the cell or body from which the motors are extracted, their specific tensions vary as M α with α not significantly different from zero. The typical specific tension found in most motors is about 200 kPa, which generalizes to individual molecular motors and microorganisms a classical property of macroscopic muscles. We propose a basic order-of-magnitude interpretation of this result.

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