Four new genera and five new species of 'Heterocypris' from Western Australia (Crustacea, Ostracoda, Cyprinotinae)

Five new species in four new genera from Western Australia are described. All species have valve characters that are reminiscent of the genus Heterocypris Claus, 1892 and also have similar valve outlines, with highly arched valves. However, all species have a hemipenis morphology that is totally different from the typical form in Heterocypris. In Patcypris gen. nov. (with type species P outback gen. et sp. nov.), the lateral lobe is large and shaped as a pickaxe, while the medial lobe is divided into two distal lobes. Trilocypris gen. nov. (with type species T. horwitzi gen. et sp. nov.) is characterised by a hemipenis that has three, instead of two, distal lobes. In Bilocypris gen. nov. (with type species B. fortescuensis gen. et sp. nov. and a second species, B. mandoraensis gen. et sp. nov.), the lateral lobe of the hemipenis is spatulate, rather than boot-shaped, and the medial lobe is bilobed. Bilicypris gen. nov. (with type species B. davisae gen. et sp. nov.) has a large and sub-rectangular lateral lobe and a pointed medial lobe. We discuss the taxonomic value of the traditional and new morphological characters and speculate that the diversity of this cluster of genera and species may be greater than currently known

Four new genera and five new species of 'Heterocypris' from Western Australia (Crustacea, Ostracoda, Cyprinotinae)

Five new species in four new genera from Western Australia are described. All species have valve characters that are reminiscent of the genus Heterocypris Claus, 1892 and also have similar valve outlines, with highly arched valves. However, all species have a hemipenis morphology that is totally different from the typical form in Heterocypris. In Patcypris gen. nov. (with type species P outback gen. et sp. nov.), the lateral lobe is large and shaped as a pickaxe, while the medial lobe is divided into two distal lobes. Trilocypris gen. nov. (with type species T. horwitzi gen. et sp. nov.) is characterised by a hemipenis that has three, instead of two, distal lobes. In Bilocypris gen. nov. (with type species B. fortescuensis gen. et sp. nov. and a second species, B. mandoraensis gen. et sp. nov.), the lateral lobe of the hemipenis is spatulate, rather than boot-shaped, and the medial lobe is bilobed. Bilicypris gen. nov. (with type species B. davisae gen. et sp. nov.) has a large and sub-rectangular lateral lobe and a pointed medial lobe. We discuss the taxonomic value of the traditional and new morphological characters and speculate that the diversity of this cluster of genera and species may be greater than currently known

ac Losses in a Finite Z Stack Using an Anisotropic Homogeneous-Medium Approximation

A finite stack of thin superconducting tapes, all carrying a fixed current I, can be approximated by an anisotropic superconducting bar with critical current density Jc=Ic/2aD, where Ic is the critical current of each tape, 2a is the tape width, and D is the tape-to-tape periodicity. The current density J must obey the constraint \int J dx = I/D, where the tapes lie parallel to the x axis and are stacked along the z axis. We suppose that Jc is independent of field (Bean approximation) and look for a solution to the critical state for arbitrary height 2b of the stack. For c<|x|<a we have J=Jc, and for |x|<c the critical state requires that Bz=0. We show that this implies \partial J/\partial x=0 in the central region. Setting c as a constant (independent of z) results in field profiles remarkably close to the desired one (Bz=0 for |x|<c) as long as the aspect ratio b/a is not too small. We evaluate various criteria for choosing c, and we show that the calculated hysteretic losses depend only weakly on how c is chosen. We argue that for small D/a the anisotropic homogeneous-medium approximation gives a reasonably accurate estimate of the ac losses in a finite Z stack. The results for a Z stack can be used to calculate the transport losses in a pancake coil wound with superconducting tape.Comment: 21 pages, 17 figures, accepted by Supercond. Sci. Techno

Distribution and Environmental Tolerances of Aquatic Macroinvertebrate Families in the Agricultural Zone of Southwestern Australia

The agricultural zone of southwestern Australia is an extensively modified landscape. Ninety percent of the perennial native vegetation has been cleared and replaced by annual cereal crops and pasture. Consequently, groundwater has risen and much of the region is affected by dryland salinity. River geomorphology and water quality have been severely impacted by land clearing, anthropogenic patterns of land use, and secondary salinization. The objectives of this study were to determine patterns of distribution of aquatic macroinvertebrates in the region, and to identify environmental variables influencing these patterns. Aquatic macroinvertebrates were sampled at 176 river sites during spring 1997 and a range of environmental data were collected at each site. Eighty-one families were collected, with the fauna being dominated by insects. At the family level, macroinvertebrate communities were homogeneous and depauperate, and consisted of families that tolerated a broad range of environmental conditions. The fauna was particularly resilient to high salinities, with some families tolerating salinities orders of magnitude greater than previously reported for lotic waters. The most significant environmental factors influencing the distribution of aquatic invertebrates were rainfall, salinity, land use, and instream habitat

Application of realistic effective interactions to the structure of the Zr isotopes

We calculate the low-lying spectra of the zirconium isotopes Z=40 with neutron numbers from N=52 to N=60 using the 1p1/20g9/2 proton and 2s1d0g7/20h11/2 neutron sub-shells to define the model space. Effective proton-proton, neutron--neutron and proton-neutron interactions have been derived using 88Sr as closed core and employing perturbative many-body techniques. The starting point is the nucleon-nucleon potential derived from modern meson exchange models. The comprehensive shell-model calculation performed in this work provides a qualitative reproduction of essential properties such as the sub-shell closures in 96Zr and 98Zr.Comment: To appear in Phys Rev C, june 2000, 8 figs, Revtex latex styl

Sender Policy Framework as a tool for SPAM reduction

A brief presentation on the Sender Policy Framework as a tool for SPAM reduction given to a community of higher education IT practitioners

Fermi Surface Properties of Low Concentration Cex_{x}La1−x_{1-x}B6_{6}: dHvA

The de Haas-van Alphen effect is used to study angular dependent extremal areas of the Fermi Surfaces (FS) and effective masses of Ce$_{x}$La$_{1-x}$B$_{6}$ alloys for $x$ between 0 and 0.05. The FS of these alloys was previously observed to be spin polarized at low Ce concentration ($x$ = 0.05). This work gives the details of the initial development of the topology and spin polarization of the FS from that of unpolarized metallic LaB$_{6}$ to that of spin polarized heavy Fermion CeB$_{6}$ .Comment: 7 pages, 9 figures, submitted to PR

Photochemical pump and NMR probe : Chemically created NMR coherence on a microsecond time scale

We report pump-probe experiments employing laser-synchronized reactions of para-hydrogen (para-H2) with transition metal dihydride complexes in conjunction with nuclear magnetic resonance (NMR) detection. The pump-probe experiment consists of a single nanosecond laser pump pulse followed, after a precisely defined delay, by a single radio frequency (rf) probe pulse. Laser irradiation eliminates H2 from either Ru(PPh3) 3(CO)(H)2 1 or cis-Ru(dppe)2(H)2 2 in C6D6 solution. Reaction with para-H2 then regenerates 1 and 2 in a well-defined nuclear spin state. The rf probe pulse produces a high-resolution, single-scan 1H NMR spectrum that can be recorded after a pump-probe delay of just 10 μs. The evolution of the spectra can be followed as the pump-probe delay is increased by micro- or millisecond increments. Due to the sensitivity of this para-H2 experiment, the resulting NMR spectra can have hydride signal-to-noise ratios exceeding 750:1. The spectra of 1 oscillate in amplitude with frequency 1101 ± 3 Hz, the chemical shift difference between the chemically inequivalent hydrides. The corresponding hydride signals of 2 oscillate with frequency 83 ± 5 Hz, which matches the difference between couplings of the hydrides to the equatorial 31P nuclei. We use the product operator formalism to show that this oscillatory behavior arises from a magnetic coherence in the plane orthogonal to the magnetic field that is generated by use of the laser pulse without rf initialization. In addition, we demonstrate how chemical shift imaging can differentiate the region of laser irradiation thereby distinguishing between thermal and photochemical reactivity within the NMR tube

O(12) limit and complete classification of symmetry schemes in proton-neutron interacting boson model

It is shown that the proton-neutron interacting boson model (pnIBM) admits new symmetry limits with O(12) algebra which break F-spin but preserves the quantum number M_F. The generators of O(12) are derived and the quantum number `v' of O(12) for a given boson number N is determined by identifying the corresponding quasi-spin algebra. The O(12) algebra generates two symmetry schemes and for both of them, complete classification of the basis states and typical spectra are given. With the O(12) algebra identified, complete classification of pnIBM symmetry limits with good M_F is established.Comment: 22 pages, 1 figur