6,097 research outputs found
Inner-complex compounds of alicyclic vic-dioximes
The need for a water-soluble vic-dioxime as an analytical reagent for nickel(II) and palladium(II) ions has long been evident. Thus, a preparation and investigation of some alicyclic vic-dioximes as possible water-soluble reagents was undertaken. Secondly, in order to obtain a better understanding of the structure of the inner-complex compounds that the vic-dioximes form with certain ions, an infrared spectroscopic study of the nature of the hydrogen bonds in these inner-complex compounds was made
Identifying invertebrate invasions using morphological and molecular analyses: North American Daphnia ‘pulex’ in New Zealand fresh waters
We used a DNA barcoding approach to identify specimens of the Daphnia pulex complex occurring in New Zealand lakes, documenting the establishment of non-indigenous North American Daphnia 'pulex'. Morphological delineation of species in this complex is problematic due to a lack of good morphological traits to distinguish the species, as there is a relatively high degree of morphological stasis within the group through evolutionary time. Accordingly, genetic analyses were used to determine the specific identity and likely geographic origin of this species. Morphologically, individuals most closely resembled Daphnia pulicaria or Daphnia pulex sensu lato, which cannot be separated morphologically. Furthermore, each of these taxa comprises separate species in North America and Europe, despite carrying the same names. We identified individuals using a 658 bp nucleotide portion of the mitochondrial cytochrome c oxidase subunit 1 gene (COI) as North American Daphnia 'pulex', being distinct from European Daphnia pulex sensu stricto and D. pulicaria from Europe or North America. Cellulose allozyme electrophoresis was used to confirm that individuals were not hybrids with D. pulicaria. North American Daphnia 'pulex' in New Zealand were first recorded in New Zealand from South Island lakes that are popular for overseas recreational fishers, indicating a possible source of introduction for this species (e.g. on/in fishing gear). Our study provides an additional example of how genetic techniques can be used for the accurate identification of non-indigenous taxa, particularly when morphological species determination is not possible. The growth of global databases such as GenBank and Barcode of Life Datasystems (BOLD) will further enhance this identification capacity
Zinc - 1,10-phenanthroline complexes and their analytical application
The use of ultraviolet spectrophotometry for quantitative inorganic analytical purposes has long remained unexploited. An extremely large number of complexes of metals have characteristic absorption properties in the visible portion of the spectrum and many colorimetric methods of analysis depend upon this fact. With the present availability of ultraviolet spectrophotometric equipment the charachteristic absorption properties of many colorless metallic complexes in the ultraviolet region of the spectrum should as conveniently be capable of similar utilization
Some bis(dialkylphosphinyl) methanes as solvent extractants
An extensive review of some of the more important neutral organophosphorus compounds as solvent extractants was given. The compounds included were tri-n-butyl phosphate, TBP, tri-n-octylphosphine oxide, TOPO, tris (2 -ethylhexyl)phosphine oxide, TEHPO, and bis (di-n-hexylphosphinyl) methane, HDPM. A review was also given on the effects of structure on the extracting power of neutral organophosphorus compounds
Quantum Black Holes
Static solutions of large- quantum dilaton gravity in dimensions are
analyzed and found to exhibit some unusual behavior. As expected from previous
work, infinite-mass solutions are found describing a black hole in equilibrium
with a bath of Hawking radiation. Surprisingly, the finite mass solutions are
found to approach zero coupling both at the horizon and spatial infinity, with
a ``bounce'' off of strong coupling in between. Several new zero mass solutions
-- candidate quantum vacua -- are also described.Comment: 14 pages + 6 figure
Model validation for a noninvasive arterial stenosis detection problem
Copyright @ 2013 American Institute of Mathematical SciencesA current thrust in medical research is the development of a non-invasive method for detection, localization, and characterization of an arterial stenosis (a blockage or partial blockage in an artery). A method has been proposed to detect shear waves in the chest cavity which have been generated by disturbances in the blood flow resulting from a stenosis. In order to develop this methodology further, we use both one-dimensional pressure and shear wave experimental data from novel acoustic phantoms to validate corresponding viscoelastic mathematical models, which were developed in a concept paper [8] and refined herein. We estimate model parameters which give a good fit (in a sense to be precisely defined) to the experimental data, and use asymptotic error theory to provide confidence intervals for parameter estimates. Finally, since a robust error model is necessary for accurate parameter estimates and confidence analysis, we include a comparison of absolute and relative models for measurement error.The National Institute of Allergy and Infectious Diseases, the Air Force Office of Scientific Research, the Deopartment of Education and the Engineering and Physical Sciences Research Council (EPSRC)
On the Interplay of Monopoles and Chiral Symmetry Breaking in Non-Compact Lattice QED
Non-compact lattice QED is simulated for various numbers of fermion species
ranging from 8 through 40 by the exact Hybrid Monte Carlo algorithm. Over
this range of , chiral symmetry breaking is found to be strongly
correlated with the effective monopoles in the theory. For between 8 and
16 the chiral symmetry breaking and monopole percolation transitions are second
order and coincident. Assuming powerlaw critical behavior, the correlation
length exponent for the chiral transition is identical to that of monopole
percolation. This result supports the conjecture that monopole percolation
``drives" the nontrivial chiral transition. For between 20 and 32, the
monopoles experience a first order condensation transition coincident with a
first order chiral transition. For as large as 40 both transitions are
strongly suppressed. The data at large N_f (N_f \mathrel {\mathpalette \vereq
>} 20) is interpreted in terms of a strongly interacting monopole gas-liquid
transition.Comment: Revtex file, 23 pages, hardcopy figures only
Nonsingular Lagrangians for Two Dimensional Black Holes
We introduce a large class of modifications of the standard lagrangian for
two dimensional dilaton gravity, whose general solutions are nonsingular black
holes. A subclass of these lagrangians have extremal solutions which are
nonsingular analogues of the extremal Reissner-Nordstrom spacetime. It is
possible that quantum deformations of these extremal solutions are the endpoint
of Hawking evaporation when the models are coupled to matter, and that the
resulting evolution may be studied entirely within the framework of the
semiclassical approximation. Numerical work to verify this conjecture is in
progress. We point out however that the solutions with non-negative mass always
contain Cauchy horizons, and may be sensitive to small perturbations.Comment: 27 pages, three figures, RU-92-61. (Replaced version contains some
corrections to incorrect equations. The zero temperature extremal geometry
(the conjectured end-point of the Hawking evaporation) is not as stated in
the previous version, but rather is a nonsingular analogue of the zero
temperature Reissner-Nordstrom space-time.
The Discovery of XY Sex Chromosomes in a \u3cem\u3eBoa\u3c/em\u3e and \u3cem\u3ePython\u3c/em\u3e
For over 50 years, biologists have accepted that all extant snakes share the same ZW sex chromosomes derived from a common ancestor [1, 2, 3], with different species exhibiting sex chromosomes at varying stages of differentiation. Accordingly, snakes have been a well-studied model for sex chromosome evolution in animals [1, 4]. A review of the literature, however, reveals no compelling support that boas and pythons possess ZW sex chromosomes [2, 5]. Furthermore, phylogenetic patterns of facultative parthenogenesis in snakes and a sex-linked color mutation in the ball python (Python regius) are best explained by boas and pythons possessing an XY sex chromosome system [6, 7]. Here we demonstrate that a boa (Boa imperator) and python (Python bivittatus) indeed possess XY sex chromosomes, based on the discovery of male-specific genetic markers in both species. We use these markers, along with transcriptomic and genomic data, to identify distinct sex chromosomes in boas and pythons, demonstrating that XY systems evolved independently in each lineage. This discovery highlights the dynamic evolution of vertebrate sex chromosomes and further enhances the value of snakes as a model for studying sex chromosome evolution
S-Wave Scattering of Charged Fermions by a Magnetic Black Hole
We argue that, classically, -wave electrons incident on a magnetically
charged black hole are swallowed with probability one: the reflection
coefficient vanishes. However, quantum effects can lead to both electromagnetic
and gravitational backscattering. We show that, for the case of extremal,
magnetically charged, dilatonic black holes and a single flavor of low-energy
charged particles, this backscattering is described by a perturbatively
computable and unitary -matrix, and that the Hawking radiation in these
modes is suppressed near extremality. The interesting and much more difficult
case of several flavors is also discussed.Comment: 9p
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