A higher order panel method for linearized supersonic flow

The basic integral equations of linearized supersonic theory for an advanced supersonic panel method are derived. Methods using only linear varying source strength over each panel or only quadratic doublet strength over each panel gave good agreement with analytic solutions over cones and zero thickness cambered wings. For three dimensional bodies and wings of general shape, combined source and doublet panels with interior boundary conditions to eliminate the internal perturbations lead to a stable method providing good agreement experiment. A panel system with all edges contiguous resulted from dividing the basic four point non-planar panel into eight triangular subpanels, and the doublet strength was made continuous at all edges by a quadratic distribution over each subpanel. Superinclined panels were developed and tested on s simple nacelle and on an airplane model having engine inlets, with excellent results

Toothed whale auditory brainstem responses measured with a non-invasive, on-animal tag

This work was funded by Grant No. N00014-20-1-2748 from the United States Office of Naval Research (ONR) awarded to M.W. Tag development was supported by ONR Grant Nos. N00014-16-1-2852, N00014-18-1-2062, and N00014-20-1-2709. M.J. was supported by the Aarhus University Research Foundation and the EU H2020 research and innovation program under Marie Skłodowska-Curie Grant No. 754513.Empirical measurements of odontocete hearing are limited to captive individuals, constituting a fraction of species across the suborder. Data from more species could be available if such measurements were collected from unrestrained animals in the wild. This study investigated whether electrophysiological hearing data could be recorded from a trained harbor porpoise (Phocoena phocoena) using a non-invasive, animal-attached tag. The results demonstrate that auditory brainstem responses to external and self-generated stimuli can be measured from a stationary odontocete using an animal-attached recorder. With additional development, tag-based electrophysiological platforms may facilitate the collection of hearing data from freely swimming odontocetes in the wild.Publisher PDFPeer reviewe

Preparation of potentially porous, chiral organometallic materials through spontaneous resolution of pincer palladium conformers

Understanding the mechanism by which advanced materials assemble is essential for the design of new materials with desired properties. Here, we report a method to form chiral, potentially porous materials through spontaneous resolution of conformers of a PCP pincer palladium complex ({; ; 2, 6-bis[(di-t-butylphosphino)methyl]phenyl}; ; palladium(II)halide). The crystallisation is controlled by weak hydrogen bonding giving rise to chiral qtz-nets and channel structures, as shown by 16 such crystal structures for X = Cl, and Br with various solvents like pentane and bromobutane. The fourth ligand (in addition to the pincer ligand) on palladium plays a crucial role ; the chloride and the bromide primarily form hexagonal crystals with large 1D channels, whereas the iodide (presumably due to its inferior hydrogen bonding capacity) forms monoclinic crystals without channels. The hexagonal channels are completely hydrophobic and filled with disordered solvent molecules. Upon heating loss of solvent occurs and the hexagonal crystals transform into other non-porous polymorphs. Also by introducing strong acid, the crystallisation process can be directed to a different course, giving several different non-porous polymorphs. In conclusion a number of rules can be formulated dictating the formation of hexagonal channel structures based on pincer palladium complexes. Such rules are important for a rational design of future self-assembling materials with applications in storage and molecular recognition

[2,6-Bis(di-tert-butyl­phosphinometh­yl)phenyl-κ3 P,C 1,P′](trifluoro­acetato)palladium(II)

The PdII atom in the title compound, [Pd(C2F3O2)(C24H43P2)], adopts a distorted square-planar geometry with the P atoms in a trans arrangement, forming two five-membered chelate rings. Four intra­molecular C—H⋯O hydrogen bonds occur. The crystal packing reveals one weak inter­molecular C—H⋯O hydrogen bond, which self-assembles the mol­ecules into infinite chains parallel to the b axis

Dimension of the Torelli group for Out(F_n)

Let T_n be the kernel of the natural map from Out(F_n) to GL(n,Z). We use combinatorial Morse theory to prove that T_n has an Eilenberg-MacLane space which is (2n-4)-dimensional and that H_{2n-4}(T_n,Z) is not finitely generated (n at least 3). In particular, this recovers the result of Krstic-McCool that T_3 is not finitely presented. We also give a new proof of the fact, due to Magnus, that T_n is finitely generated.Comment: 27 pages, 9 figure

Generators for the hyperelliptic Torelli group and the kernel of the Burau representation at t = -1

We prove that the hyperelliptic Torelli group is generated by Dehn twists about separating curves that are preserved by the hyperelliptic involution. This verifies a conjecture of Hain. The hyperelliptic Torelli group can be identified with the kernel of the Burau representation evaluated at t = −1 and also the fundamental group of the branch locus of the period mapping, and so we obtain analogous generating sets for those. One application is that each component in Torelli space of the locus of hyperelliptic curves becomes simply connected when curves of compact type are added

Bis(1,3-dimesitylimidazol­yl)gold(I) 2,4,8,10-tetra­phenyl-1,3,5,7,9,11-hexa­oxa-2,4,8,10-tetra­bora-6-borataspiro­[5.5]undeca­ne

The AuI atom in the title compound, [Au(C21H24N2)2](C24H20B5O6), adopts a slightly distorted linear AuC2 coordination geometry arising from its coordination by two mesitylenic N-heterocyclic carbene ligands, forming an overall cationic complex. The dihedral angle between the imidazole rings is 57.3 (6)°. In the crystal, the components are linked by weak C—H⋯O hydrogen bonds

Sperm whale codas may encode individuality as well as clan identity

The research was funded by the Danish Research Council; the Carlsberg Foundation; Fundação para a Ciência e a Tecnologia (FCT); Fundo Regional da Ciência, Tecnologia (FRCT) through research projects TRACE-PTDC/MAR/74071/2006 and MAPCET-M2.1.2/F/012/2011 [Fundo Europeu de Desenvolvimento Regional, the Competitiveness Factors Operational (COMPETE), Quadro de Referência Estratégico Nacional (QREN) European Social Fund, and Proconvergencia Açores/European Union Program]; Aarhus University; Woods Hole Oceanographic Institution; University of Southern Denmark and University of La Laguna. We acknowledge funds provided by FCT to MARE – Marine and Environmental Sciences Centre (UID/MAR/04292/2013) and Instituto do Mar at University of the Azores and by the FRCT – Government of the Azores pluriannual funding. C.O. was funded by FCT (SFRH/BD/37668/2007). M.A.S. was supported by an FCT postdoctoral grant (SFRH/BPD/29841/2006) and is currently supported by POPH, QREN European Social Fund and the Portuguese Ministry for Science and Education, through an FCT Investigator grant. M.J. is supported by the Marine Alliance for Science and Technology Scotland (MASTS) and a Marie Curie Career Integration Grant. D.M.W. was funded by a Ph.D. stipend from the Oticon Foundation, Denmark.Sperm whales produce codas for communication that can be grouped into different types according to their temporal patterns. Codas have led researchers to propose that sperm whales belong to distinct cultural clans, but it is presently unclear if they also convey individual information. Coda clicks comprise a series of pulses and the delay between pulses is a function of organ size, and therefore body size, and so is one potential source of individual information. Another potential individual-specific parameter could be the inter-click intervals within codas. To test whether these parameters provide reliable individual cues, stereo-hydrophone acoustic tags (Dtags) were attached to five sperm whales of the Azores, recording a total of 802 codas. A discriminant function analysis was used to distinguish 288 5 Regular codas from four of the sperm whales and 183 3 Regular codas from two sperm whales. The results suggest that codas have consistent individual features in their inter-click intervals and inter-pulse intervals which may contribute to individual identification. Additionally, two whales produced different coda types in distinct foraging dive phases. Codas may therefore be used by sperm whales to convey information of identity as well as activity within a social group to a larger extent than previously assumed.Publisher PDFPeer reviewe

Morphology and reproduction in the Hapalocarcinus marsupialis Stimpson, 1859 species complex (Decapoda: Brachyura: Cryptochiridae)

Symbiotic relationships contribute considerably to the high biodiversity found on coral reefs. Coral-dwelling gall crabs (Cryptochiridae) represent a prime example of coral-associated invertebrates that exhibit obligate relationships with their host. The induction of a skeletal modification in the coral, used as a dwelling by the crab, is the most remarkable aspect of this close association. Here we examined Hapalocarcinus marsupialisStimpson, 1859, collected from Pocillopora and Stylophora corals in the Saudi Arabian Red Sea. Specimens were DNA barcoded, and five distinct clades were revealed, providing further evidence for the hypothesis that H. marsupialis is a species complex. Divergence (COI) between the clades ranged from 3.2 to 15.7%. The putative species were tested for differences in morphology and reproduction. Crabs were examined regarding morphometric characters (carapace length and width, pleon (abdomen), chelae, and growth patterns) and reproductive traits. The data were pooled and analysed by host genus and putative species, which revealed significant differences for most of the measured variables in female crabs. Specimens retrieved from Pocillopora were significantly larger (up to 49 %) and had higher fecundity than those inhabiting Stylophora. For reproductive output (RO) no differences at species- or host-genus level were detected. The average RO of ~70% over all specimens is high compared to other brachyurans, supporting the assumption that symbiotic brachyurans invest more energy in reproduction than their free-living counterparts. Discrepancies with published data on growth and reproduction of Hapalocarcinus are discussed. Our results demonstrate the usefulness of morphometric traits and fecundity in separating the clades in the H. marsupialis complex, and prepare the ground for further morphometric studies on the genus and other symbiotic brachyurans. Moreover, it highlights the need to check for the presence of cryptic species when studying aspects of the biology of a species