bluuebunny/crossref_metadata_2025 huggingface dataset:
Grain Boundary Precipitation in Oxide Systems
Authors: Stubican V. S. , Viechnicki D.
Published: April 2005

The spatial distribution of precipitate in several polycrystalline oxide systems after annealing of the crystalline solutions was investigated by using an electron probe microanalyzer. Preferential grain boundary and intergranular voids precipitation of the minor component was found in the majority of systems with limited crystalline solubility, e.g., MgO–Al2O3, MgO–CaO, UO2–CaO, CaO–Yb2O3, as well as with the ZrO2–MgO system which has an eutectoid. The formation of an intermediate phase during the precipitation may have a varied effect on the contribution of the surface free energy to the activation energy for nucleation. The intermediate phase appears in both MgAl2O4–Al2O3 and CaO–Yb2O3 systems, although complete phase separation occurs in the former and grain boundary precipitation in the latter.
Acoustoelectric Current Distribution and Current Saturation in CdS
Authors: McFee J. H. , Tien P. K.
Published: April 2005

The spatial distribution of electric field in photoconductive CdS is measured under the condition of current saturation. The presence of stationary high-field domains is related to the distribution of acoustoelectric current which, assuming Weinreich's relation holds, may in turn be related to the nonuniform growth and decay of acoustic energy in the samples. Detailed measurements on both homogeneous and inhomogeneous samples yield a better understanding of the mechanisms responsible for the current saturation and also provide a new method for determining the effective drift mobility of the carriers.
A Quantitative Method for the Study of Orientation Relationship between Subgrains by Dark-Field Transmission Electron Microscopy
Authors: Koo R. C.
Published: April 2005

An experiment has been carried out to demonstrate that the orientation relationship between subgrains can be deduced from dark-field microscopy. When a specimen is tilted in dark field with a g vector perpendicular to the tilting axis, contrast reversal occurs between neighboring subgrains if they are joined by a simple twist boundary parallel to g, or by a simple tilt boundary perpendicular to g. It is also shown that the tilt and twist components of a mixed boundary can be determined quantitatively by repeating the tilting experiment with different g vectors. The precision of this method and its advantages and disadvantages for quantitative studies of low-angle boundaries are evaluated from various considerations.
Radio Frequency Breakdown in Penning Geometries with Nonlinear Fields
Authors: Karras Thomas W.
Published: April 2005

Radio frequency breakdown in air (10−3 to 10−6 Torr) is studied analytically and experimentally for two electrode configurations which lead to nonlinear Mathieu-like differential equations for the confined electron motion. Experimental data are identified with two energy-gain mechanisms which are described as the collisional and resonance modes. Breakdown voltages are predicted from stability plots which show several resonance minima where the observed rf breakdown voltages are very low. Resonance minima predicted by a linear analysis are shifted by nonlinear effects, from which it is shown that the collisional mode is apparently triggered by excitation of the 7.7-eV level of the nitrogen molecule with subsequent electron emission from the cathode surface. The resonance mode is found to be largely surface independent.
Calculations for Capacitor-Driven RLC Circuits Including the Penetration of Fields into Conductors
Authors: Baker D. A. , MacRoberts M. D. J. , Mann L. W.
Published: April 2005

Calculations of the current which flows in a capacitor-driven RLC circuit have been made which include the effects of the transient diffusion of fields into load conductors. A set of dimensionless curves are given which allow prediction of the peak current in inductive loads formed by solid conductors with circular cross sections. Comparisons of these results with those based on ac skin depth approximations are made.
Electric Field Effects in Trapping Processes
Authors: Dussel Gustavo A. , Bube Richard H.
Published: April 2005

The effects of moderate electric fields (≤3×103 V/cm) on the trapping processes in photosensitive CdS-CdSe single crystals have been investigated using photoelectronic techniques. Possible mechanisms such as injection of electrons, extraction of holes, dielectric polarization due to inhomogeneities, Joule heating, electrochemical effects, impact ionization, field-assisted tunneling, and field-associated changes in the capture cross sections and/or thermal emission probabilities of traps are considered. Evidence is presented for the reality of field-associated changes in trapping parameters in the absence of all the other possible effects. Results are consistent with a field emptying of Coulomb-attractive traps by a decrease in the trap depth and a decrease in the capture cross section of traps. The conclusions may be relevant to the interpretation of space-charge-limited current data and to mechanisms capable of leading to improved photoconductor speed for low intensity excitation.
Coalescence of Two Spheres by Surface Diffusion
Authors: Nichols F. A.
Published: April 2005

A numerical solution has been obtained which gives the morphological changes and kinetics during the coalescence of two spheres by surface diffusion. The solution may be utilized for determining surface diffusion coefficients by observing the coalescence of two gas bubbles within a solid or interfacial diffusivities by observing the same phenomenon involving spherical precipitates in a solid matrix. The former parameters are of great interest in the fission-gas swelling of nuclear fuels whereas the latter figure prominently in various transformations in the solid state. The present analysis provides a theoretical framework by which these parameters may be determined under conditions of minimal absorption difficulties, as well as guidelines for applicability of the results.
Ultrasonic Attenuation near the Néel Temperature of Chromium
Authors: O'Brien E. J. , Franklin J.
Published: April 2005

It has been known for several years that single crystals of chromium display a narrow peak in the ultrasonic attenuation at temperatures near the Néel temperature. There are presented detailed measurements of the attenuation of longitudinal waves which were made to ascertain whether the peak could be explained by a temperature-dependent relaxation time. The attenuation was found to increase linearly with frequency for temperatures above the peak, and was not a simple function of frequency at lower temperatures. In either case, a simple relaxation mechanism appears not to operate, and a theory developed specifically for chromium seems necessary. The temperature dependence of the attenuation above the peak temperature follows a Gaussian falloff and is probably attributable to inhomogenieties, which smear out the local Néel temperatures.
Sputtering Yields of Several Semiconducting Compounds under Argon Ion Bombardment
Authors: Comas James , Cooper C. Burleigh
Published: April 2005

Sputtering yields of single crystals of SiC, InSb, GaAs, GaP, CdS, and PbTe under argon ion bombardment have been measured. The energy of the argon ions, obtained from a magnetically confined argon arc, ranged from 75 to 600 eV. The sputtering yields were determined from target weight losses measured by an in situ quartz spring microbalance. Yields at 500-eV argon ion energy ranged from 0.40 for SiC to 1.30 for PbTe.
Frequency of Corona Discharge Trichel Pulses in Air Flows
Authors: Nygaard Kaare J.
Published: April 2005

A phenomenological study was made to determine to what extent air streams affect electrical discharges between a negative needle and a plane at atmospheric pressure. When such discharges were operated at a constant current, first in still air and then with a wind blowing in the direction perpendicular to the gap axis, it was found that a lesser voltage was required to maintain the constant current in the latter case. In general, the repetition frequency of Trichel pulses is known to be approximately proportional to the gap current. We found that the blowing of a wind between the electrodes resulted in a pronounced decrease in the frequency, i.e., an increase in the average number of charges per pulse at constant gap current. These observations demonstrate the effect of current enhancement in windblown coronas, a phenomenon which is due to the removal of the negative ions which tend to reduce the electric field in the vital cathode region.
Evidence by Lorentz Microscopy for Magnetically Active Stacking Faults in MnAl Alloy
Authors: Zijlstra H. , Haanstra H. B.
Published: April 2005

In the ordered MnAl crystal containing magnetic atoms which are coupled ferromagnetically, stacking faults are postulated through which an antiferromagnetic coupling exists between the atoms on either side of the fault. These account for the anomalous magnetic behavior of fine MnAl powder. Such faults give rise to a domain structure the walls of which are strongly pinned to these crystallographic defects. A direct evidence for the occurrence of these stacking faults is obtained by using Lorentz electron microscopy, whereby shadow patterns of opaque MnAl particles show a characteristic distortion of their contours when the microscope is used out of focus. The distortion is interpreted in terms of stray fields due to the domain structure.

By using either the normal objective lens, which is an immersion lens, or the diffraction lens, the pattern can be studied with or without a strong applied field. Fields up to 9000 Oe could be applied. Domain structures were observed that showed a remarkable indifference for these fields. This rigidity is explained by assuming that the walls are pinned to stacking faults.

Domain structures with a high pole density on the walls were also observed. These structures are unfavorable owing to large magnetostatic energy. Their occurrence is also explained by the presence of stacking faults.
Analysis of the Thermionic Emission from Barium Telluride
Authors: Brown Howard M. , Hensley Eugene B.
Published: April 2005

The thermionic emission from barium telluride in various states of activation has been measured using cathodes formed by the direct reaction of the elements and by the reduction of barium tellurate. The data are presented in the form of effective work function plots. A method of analyzing thermionic emission data by comparing effective work function plots with curves calculated from models of the electronic structure of the material is described. Using this technique, barium telluride was found to have an electron affinity of 1.5±0.2 eV, a donor at about 2.2 eV below the vacuum level and a second donor of lower density about 3.2 eV below the vacuum level.
Thermionic Converters Operating in the Ignited Mode. Part II: A Quasi-Equilibrium Model for the Interelectrode Plasma
Authors: Wilkins Daniel R. , Gyftopoulos Elias P.
Published: April 2005

A multistage ionization-recombination model is proposed to describe the formation and loss of atomic ions in low-energy cesium plasmas. Solutions of the ambipolar diffusion equation are investigated with due consideration given to these processes. The solutions indicate the existence of a state of quasi-equilibrium throughout most of a low-energy plasma in which the electron temperature is more than several hundred degrees above a critical ignition temperature.

The assumption of quasi-equilibrium in the interelectrode plasma of a thermionic converter operating in the collisional ignited mode is shown to result in a plasma model which correlates a wide variety of experimental data. Included in the successful correlations are electron random current density and temperature profiles as well as output-current characteristics.

The experimentally observed state of quasi-equilibrium in thermionic converter plasmas is found to be near the Saha-equilibrium limit. It is therefore concluded that the multistage ionization-recombination processes in these plasmas involve numerous excited states.
Auxiliary basis expansions for large-scale electronic structure calculations
Authors: Jung Yousung , Sodt Alex , Gill Peter M. W. , Head-Gordon Martin
Published: April 2005

One way to reduce the computational cost of electronic structure calculations is to use auxiliary basis expansions to approximate four-center integrals in terms of two- and three-center integrals, usually by using the variationally optimum Coulomb metric to determine the expansion coefficients. However, the long-range decay behavior of the auxiliary basis expansion coefficients has not been characterized. We find that this decay can be surprisingly slow. Numerical experiments on linear alkanes and a toy model both show that the decay can be as slow as 1/
r
in the distance between the auxiliary function and the fitted charge distribution. The Coulomb metric fitting equations also involve divergent matrix elements for extended systems treated with periodic boundary conditions. An attenuated Coulomb metric that is short-range can eliminate these oddities without substantially degrading calculated relative energies. The sparsity of the fit coefficients is assessed on simple hydrocarbon molecules and shows quite early onset of linear growth in the number of significant coefficients with system size using the attenuated Coulomb metric. Hence it is possible to design linear scaling auxiliary basis methods without additional approximations to treat large systems.
A positive feedback vector for identification of nucleotide sequences that enhance translation
Authors: Zhou Wei , Edelman Gerald M. , Mauro Vincent P.
Published: April 2005

In earlier studies, we identified short (6- to 22-nt) sequences that functioned as internal ribosome entry sites (IRESes) and enhanced translation. The size of these IRES elements suggested that they might be prevalent within the messenger population and that individual elements might affect the translation of different groups of mRNAs. To begin to assess the number of different IRES elements in mammalian cells, we have developed a powerful method that uses a positive feedback mechanism to amplify the activities of individual IRES elements. This method uses a vector that encodes a dicistronic mRNA with a reporter gene (
Renilla
luciferase or the EGFP) as the first cistron and the yeast Gal4/viral protein 16 (VP16) transcription factor as the second cistron. Transcription of this mRNA is driven by a minimal promoter containing four copies of the Gal4 upstream activation sequence. In this method, the presence of an IRES in the intercistronic region facilitates the translation of Gal4/VP16, which binds to the upstream activation sequences and triggers a positive feedback loop that escalates the production of dicistronic mRNA and Gal4/VP16. A corresponding increase in the translation of the first cistron (luciferase or EGFP) is monitored either by measuring luciferase activity or by using FACS. The latter enables IRES-positive cells to be isolated. We present tests of the feedback mechanism by using an IRES module from
Gtx
homeodomain mRNA and an IRES from hepatitis C virus and demonstrate the utility of this vector system for the screening, identification, and analysis of IRES elements.
Genes required for rapid expression of nitrogenase activity in
Azotobacter vinelandii
Authors: Curatti Leonardo , Brown Carolyn S. , Ludden Paul W. , Rubio Luis M.
Published: April 2005

Rnf proteins are proposed to form membrane-protein complexes involved in the reduction of target proteins such as the transcriptional regulator SoxR or the dinitrogenase reductase component of nitrogenase. In this work, we investigate the role of
rnf
genes in the nitrogen-fixing bacterium
Azotobacter vinelandii
. We show that
A. vinelandii
has two clusters of
rnf
-like genes:
rnf1
, whose expression is
nif
-regulated, and
rnf2
, which is expressed independently of the nitrogen source in the medium. Deletion of each of these gene clusters produces a time delay in nitrogen-fixing capacity and, consequently, in diazotrophic growth. Δ
rnf
mutations cause two distinguishable effects on the nitrogenase system: (
i
), slower
nifHDK
gene expression and (
ii
), impairment of nitrogenase function. In these mutants, dinitrogenase reductase activity is lowered, whereas dinitrogenase activity remains essentially unaltered. Further analysis indicates that Δ
rnf
mutants accumulate an inactive and iron-deficient form of NifH because they have lower rates of incorporation of [4Fe-4S] into NifH. Δ
rnf
mutations also cause a noticeable decrease in aconitase activity; however, they do not produce general oxidative stress or modification of Fe metabolism in
A. vinelandii
. Our results suggest the existence of a redox regulatory mechanism in
A. vinelandii
that controls the rate of expression and maturation of nitrogenase by the activity of the Rnf protein complexes.
rnf1
plays a major and more specific role in this scheme, but the additive effects of mutations in
rnf1
and
rnf2
indicate the existence of functional complementation between the two homologous systems.
β-TrCP recognizes a previously undescribed nonphosphorylated destruction motif in Cdc25A and Cdc25B phosphatases
Authors: Kanemori Yoshinori , Uto Katsuhiro , Sagata Noriyuki
Published: April 2005

β-TrCP, the F-box protein of the SCF
β-TrCP
ubiquitin ligase (SCF, Skp1/Cul1/F-box protein), recognizes the doubly phosphorylated DSG motif (DpSGΦXpS) in various SCF
β-TrCP
target proteins. The Cdc25A phosphatase, a key cell-cycle regulator in vertebrate cells, undergoes a rapid ubiquitin-dependent degradation in response to genotoxic stress. β-TrCP binds to the DSG motif of human Cdc25A in a manner dependent on Chk1 and other unknown kinases. However,
Xenopus
Cdc25A does not have a DSG motif at the corresponding site of human Cdc25A. Here, we report that both
Xenopus
Cdc25A and human Cdc25A have a previously undescribed nonphosphorylated DDG motif (DDGΦXD) for recognition by β-TrCP. When analyzed by using
Xenopus
eggs, the binding of β-TrCP to the DDG motif is essential for the Chk1-induced ubiquitination and degradation of
Xenopus
Cdc25A and also plays a role in the degradation of human Cdc25A. The DDG motif also exists in human Cdc25B phosphatase (another key cell-cycle regulator), binds β-TrCP strongly, and is essential for the ubiquitination and degradation of the (labile) phosphatase in normal conditions. We provide strong evidence that, in both Cdc25A and Cdc25B, the binding (efficiency) of β-TrCP to the DDG motif is regulated by nearby residues, while ubiquitination is regulated by other events in addition to the β-TrCP binding. Finally, our additional data suggest that β-TrCP may recognize nonphosphorylated DDG-like motifs in many other proteins, including X11L (a putative suppressor of β-amyloid production) and hnRNP-U (a pseudosubstrate of SCF
β-TrCP
).
Descent representations and multivariate statistics
Authors: Adin Ron , Brenti Francesco , Roichman Yuval
Published: April 2005

Combinatorial identities on Weyl groups of typesAAandBBare derived from special bases of the corresponding coinvariant algebras. Using the Garsia-Stanton descent basis of the coinvariant algebra of typeAAwe give a new construction of the Solomon descent representations. An extension of the descent basis to typeBB, using new multivariate statistics on the group, yields a refinement of the descent representations. These constructions are then applied to refine well-known decomposition rules of the coinvariant algebra and to generalize various identities.
Signature of relations in mapping class groups and non-holomorphic Lefschetz fibrations
Authors: Endo Hisaaki , Nagami Seiji
Published: April 2005

We introduce the notion of signature for relations in mapping class groups and show that the signature of a Lefschetz fibration over the 2-sphere is the sum of the signatures for basic relations contained in its monodromy. Combining explicit calculations of the signature cocycle with a technique of substituting positive relations, we give some new examples of non-holomorphic Lefschetz fibrations of genus

3
,
4

3, 4

and

5
5

which violate slope bounds for non-hyperelliptic fibrations on algebraic surfaces of general type.
An approximate universal coefficient theorem
Authors: Lin Huaxin
Published: April 2005

An approximate Universal Coefficient Theorem (AUCT) for certain

C
∗

C^*

-algebras is established. We present a proof that Kirchberg-Phillips’s classification theorem for separable nuclear purely infinite simple

C
∗

C^*

-algebras is valid for

C
∗

C^*

-algebras satisfying the AUCT instead of the UCT. It is proved that two versions of AUCT are in fact the same. We also show that

C
∗

C^*

-algebras that are locally approximated by

C
∗

C^*

-algebras satisfying the AUCT satisfy the AUCT. As an application, we prove that certain simple

C
∗

C^*

-algebras which are locally type I are in fact isomorphic to simple AH-algebras. As another application, we show that a sequence of residually finite-dimensional

C
∗

C^*

-algebras which are asymptotically nuclear and which asymptotically satisfies the AUCT can be embedded into the same simple AF-algebra.
Telescoping, rational-valued series, and zeta functions
Authors: Ash J. , Catoiu Stefan
Published: April 2005

We give an effective procedure for determining whether or not a series

∑

n
=
M

N

r

(
n
)

\sum _{n=M}^{N}r\left ( n\right )

telescopes when

r

(
n
)

r\left ( n\right )

is a rational function with complex coefficients. We give new examples of series

(
∗
)

∑

n
=
1

∞

r

(
n
)

\left ( \ast \right ) \sum _{n=1}^{\infty }r\left ( n\right )

, where

r

(
n
)

r\left ( n\right )

is a rational function with integer coefficients, that add up to a rational number. Generalizations of the Euler phi function and the Riemann zeta function are involved. We give an effective procedure for determining which numbers of the form

(
∗
)

\left ( \ast \right )

are rational. This procedure is conditional on 3 conjectures, which are shown to be equivalent to conjectures involving the linear independence over the rationals of certain sets of real numbers. For example, one of the conjectures is shown to be equivalent to the well-known conjecture that the set

{
ζ

(
s
)

:
s
=
2
,
3
,
4
,
…
}

\left \{ \zeta \left ( s\right ) :s=2,3,4,\dots \right \}

is linearly independent, where

ζ

(
s
)

=
∑

n

−
s

\zeta \left ( s\right ) =\sum n^{-s}

is the Riemann zeta function. Some series of the form

∑

n

s

(

n
r

,

n
+
1

r

,
⋯
,

n
+
k

r

)

\sum _{n}s\left ( \sqrt [r]{n},\sqrt [r]{n+1} ,\cdots ,\sqrt [r]{n+k}\right )

, where

s
s

is a quotient of symmetric polynomials, are shown to be telescoping, as is

∑
1

/

(
n
!
+

(
n
−
1
)

!
)

\sum 1/(n!+\left ( n-1\right ) !)

. Quantum versions of these examples are also given.
The smoothing property for a class of doubly nonlinear parabolic equations
Authors: Ebmeyer Carsten , Urbano José
Published: April 2005

We consider a class of doubly nonlinear parabolic equations used in modeling free boundaries with a finite speed of propagation. We prove that nonnegative weak solutions satisfy a smoothing property; this is a well-known feature in some particular cases such as the porous medium equation or the parabolicpp-Laplace equation. The result is obtained via regularization and a comparison theorem.
Regular domains in homogeneous groups
Authors: Monti Roberto , Morbidelli Daniele
Published: April 2005

We study John, uniform and non-tangentially accessible domains in homogeneous groups of steps 2 and 3. We show that

C

1
,
1

C^{1,1}

domains in groups of step 2 are non-tangentially accessible and we give an explicit condition which ensures the John property in groups of step 3.
Food and reproduction of Trichomycterus itacarambiensis, cave catfish from south‐eastern Brazil
Authors: Trajano E.
Published: April 2005

Trichomycterus itacarambiensis is a troglobitic (cave‐restricted) catfish found in the Olhos ďÁgua Cave, Itacarambi Co., Minas Gerais, south‐eastern Brazil. The cave is subject to a pronounced seasonality, and is flooded during part of the rainy season. The pigmentation degree is variable in T. itacarambiensis, a third of the population being true albinos; the eyes vary from normal to externally invisible. As expected for a cave‐dwelling fish, T. itacarambiensis is a carnivorous generalist, which preys mainly on autochthonous insects and earthworms. It is a chemically oriented predator of bottom and surface animals, using foraging tactics also used by other cave catfishes, such as the pimelodids Pimelodella kronei and Imparfinis sp. However, bottom feeding seems to be more important for T. itacarambiensis than for the latter. There is a severe feeding stress during the dry season, when few individuals are able to get food. Reproduction is seasonal, with increased reproductive activity at the end of the rainy period, as recorded for Imparfinis sp., also a species living in a semi‐arid region with a well‐defined dry season. It is estimated that up to 50% of the female T. itacarambiensis can reproduce every year, a high proportion for a troglobitic fish species. At least during the study period, pigmented individuals reproduced more frequently than the albinos.
Genetic divergence at the NAD +‐dependent malic enzyme locus in Atlantic salmon from Europe and North America
Authors: Verspoor E. , McCcarthy E.
Published: April 2005

The distribution of genetic variation for NAD+ malic enzyme (ME*) polymorphism in the Atlantic salmon was assessed in both anadromous and resident populations. The analysis revealed a major allelic divergence between North America and Europe. The *80 variant occurred in 39 of 40 North American samples, ranging in frequency from 0 to 0.515. In contrast, it was detected in only three fish from two of the 35 European locations analysed. Eleven fish from two rivers in north‐west France had the *110 variant. While heterogeneity among North American populations was significant, no regional differentiation was apparent and anadromous and resident salmon were not found to differ.
Reproductive cycling and fecundity estimation in the upland bully
Authors: McDowall R. M. , Eldon G. A.
Published: April 2005

The upland bully is a prolific and widespread member of New Zealand freshwater fish communities that may mature at age 1 (or earlier). It begins spawning in spring, laying as many as eight clutches of eggs over the spring and summer, at periods as brief as 13 days. Ovaries contain two modes of maturing oocytes, so that oogenesis must be continual during the spawning season. This poses difficulties in fecundity estimation, which were solved by captive rearing. The ovoid eggs are about 2 mm long; egg size declines with clutch number during the summer, but increases with fish size. Clutch size varied, in 70 spawnings, from 121 to 880 eggs, with total seasonal fecundity up to >5000 eggs. The production of multiple clutches greatly increases seasonal fecundity and may explain the success of this species in sometimes unreliable or harsh environments.
Seasonal variation in condition, growth and food habits of walleye in a Great Plains reservoir and simulated effects of an altered thermal regime
Authors: Quist M. C. , Guy C. S. , Bernot R. J. , Stephen J. L.
Published: April 2005

Catch rates in gillnets and relative weight (Wr) of walleye Stizostedion vitreum, in Glen Elder Reservoir, Kansas, were lowest during the summer (June–August) and highest during the autumn (September–November). Approximately 80% of their annual growth in length and mass was attained during late summer and autumn. Growth was minimal during winter (January–February) and spring (March–May). The number of walleye with empty stomachs was highest during the summer. Invertebrates (Cladocera, Chironomidae) were common in walleye stomachs during the summer and spring, but contributed little to the ingested biomass. Gizzard shad Dorosoma cepedianum dominated walleye diets (per cent by mass) throughout the year. A bioenergetics model predicted that the proportion of maximum consumption (Pc) was highest during the autumn and was probably due to spatial overlap of walleye and gizzard shad once water temperatures were <22° C. The bioenergetics model predicted that walleye would lose up to 65% of their body mass during the summer if water temperature increased by 10% (as predicted by some global warming models). Growth during the autumn, winter and spring was enhanced up to 150% by increased temperatures. The results of this study indicate that lower condition, reduced consumption and slow growth are a generalized response of walleye to extreme temperatures. Elevated temperatures may have a net positive effect on walleye growth if they can survive the high thermal stress during summer.
Different iodine and thyroid hormone levels between Atlantic halibut larvae fed wild zooplankton or Artemia from first exogenous feeding until post metamorphosis
Authors: Solbakken J. S. , Berntessen M. H. G. , Norberg B. , Pittman K. , Hamre K.
Published: April 2005

The iodine concentration in wild zooplankton was 700 times higher than in Artemia and threefold higher in Atlantic halibut Hippoglossus hippoglossus larvae fed wild zooplankton than in those fed Artemia. In larvae fed wild zooplankton thyroxine (T4) and triiodothyronine (T3) concentrations were significantly higher than in those fed Artemia at the commencement of metamorphosis, 68–77 days post hatching. There was no difference in the amino acids phenylalanine and tyrosine levels in larvae fed Artemia in comparison with those fed wild zooplankton. The selenium level was significantly higher in larvae fed Artemia than in those fed wild zooplankton, but concentrations in the prey were not different. The results indicate sufficient amounts of phenylalanine, tyrosine and selenium in Artemia, but indicated a lower thyroid status due to an insufficient iodine supply at commencement of metamorphosis in larvae fed Artemia. This may partly explain the higher frequency of juveniles with complete eye migration and asymmetric pigmentation in the group fed wild zooplankton.
Glycoconjugate characterization in the intestine of Umbrina cirrosa by means of lectin histochemistry
Authors: Pedini V. , Scocco P. , Gargiulo A. M. , Ceccarelli P. , Lorvik S.
Published: April 2005

Goblet cells in the intestine of shi drum Umbrina cirrosa showed the presence of glycoconjugates particularly rich in fucose and N‐acetylglucosamine residues. They displayed also sialic acid linked to galactosyl(β1→3)N‐acetylgalactosamine and to galactosyl(β1→4)N‐acetylglucosamine. All the nine horseradish peroxidase‐conjugated lectins employed with the only exception of GSA II marked the enterocytes supranuclear region and the cell coat; the cell coat showed a more intense reactivity toward the different lectins, particularly enhanced with the use of fucosyl specific lectins.
Ontogenetic shift in nocturnal microhabitat selection by giant kokopu in a New Zealand stream
Authors: Whitehead A. L. , David B. O. , Closs G. P.
Published: April 2005

Nocturnal microhabitat selection in relation to size was examined for a New Zealand drift‐feeding freshwater fish, the giant kokopu Galaxias argenteus in three coastal Otago streams. Evidence for ontogenetic shifts in microhabitat selection were observed, particularly with respect to water velocity and depth. Small (<80 mm) giant kokopu tended to occur in shallow backwaters adjacent to fast flowing water. In contrast, larger individuals (≥80 mm) were most commonly observed in deeper, slower flowing pools. These patterns of habitat selection are most likely associated with the trade‐offs involved with the selection of optimal habitats for drift feeding combined with avoidance of intra‐specific competition and the threat of predation from larger conspecifics.
Fish recruitment in a canal with intensive navigation: implications for ecosystem management
Authors: Arlinghaus R. , Engelhardt C. , Sukhodolov A. , Wolter C.
Published: April 2005

The young‐of‐the‐year (YOY) fish community in Oder‐Havel‐Kanal, a navigable canal in the German lowlands, assessed from May to October 1999, was dominated by tolerant species especially roach Rutilus rutilus and perch Perca fluviatilis. Roach dominance was high in May and June and low during the rest of the sampling period. The dominance pattern of perch was inversely related to that of roach. Significantly higher densities of significantly smaller YOY fishes were found in bays compared with the straight reaches of the main channel which was the result of an aggregation of 0+ year roach in bays in May and June. Parallel to low structural variability (spawning and nursery habitats), the intensive ship traffic may have been a major force structuring the fish communities in the canals. Measured ship‐induced flow velocity in straight reaches was about four times higher than in bays of the canal. Maximum flow velocities caused by barge tows were also four times higher than those induced by pleasure boats. The study demonstrated the relatively low fish reproductive potential of a navigable, artificially embanked lowland canal. To improve fish reproduction, modification of canal banks is highly advisable to preserve existing bays and tributaries and even to create additional ones.
Individual rainbow trout can learn and anticipate multiple daily feeding times
Authors: Chen W.‐M. , Tabata M.
Published: April 2005

The present study was conducted to investigate whether individual rainbow trout Oncorhynchus mykiss can simultaneously anticipate two daily meals, and to evaluate the influence of time‐restricted feeding schedules and light‐dark (L:D) cycles on the timing of self‐feeding activity. Individual rainbow trout were capable of anticipating not only a single meal but also two daily meals scheduled at different times; the duration of anticipation was short and precise. This seems to be the first convincing evidence to show that a single fish can simultaneously anticipate two daily meals. Change in the onset and cessation of light did not affect the duration of food‐anticipatory activity, although it led to shift the phases of the light‐related self‐feeding activity. Moreover, under constant light and ad lib feeding conditions, only one band of rhythmic activity was observed in individual rainbow trout that had previously developed food‐anticipatory activity to each of the two daily meals.
Phylogenetic relationships of Moxostoma and Scartomyzon (Catostomidae) based on mitochondrial cytochrome b sequence data
Authors: Harris P. M. , Mayden R. L. , Espinosa Pérez H. S. , de Leon F. García
Published: April 2005

A recent phylogenetic study based on morphological, biochemical and early life history characters resurrected the genus Scartomyzon (jumprock suckers, c. eight−10 species) from Moxostoma (redhorse suckers, c. 10–11 species) and advanced the understanding of relationships among species in these two genera, and the genealogical affinities of these genera with other evolutionary lineages within the tribe Moxostomatini in the subfamily Catostominae. To further examine phylogenetic relationships among moxostomatin suckers, the complete mitochondrial (mt) cytochrome b gene was sequenced from all species within this tribe and representative outgroup taxa from the Catostomini and other catostomid subfamilies. Phylogenetic analysis of gene sequences yielded two monophyletic clades within Catostominae: Catostomus+Deltistes+Xyrauchen+Erimyzon+Minytrema and Moxostoma+Scartomyzon+Hypentelium+Thoburnia. Within the Moxostomatini, Thoburnia was either unresolved or polyphyletic; Thoburnia atripinnis was sister to a monophyletic Hypentelium. In turn, this clade was sister to a monophyletic clade containing Scartomyzon and Moxostoma. Scartomyzon was never resolved as monophyletic, but was always recovered as a polyphyletic group embedded within Moxostoma, rendering the latter genus paraphyletic if ‘Scartomyzon’ continues to be recognized. Relationships among lineages within the Moxostoma and‘Scartomyzon’clade were resolved as a polytomy. To better reflect phylogenetic relationships resolved in this analysis, the following changes to the classification of the tribe Moxostomatini are proposed: subsumption of‘Scartomyzon’into Moxostoma; restriction of the tribe Moxostomatini to Moxostoma; resurrect the tribe Erimyzonini, containing Erimyzon and Minytrema, classified as incertae sedis within Catostominae; retain the tribe Thoburniini.
Sexual and geographical variation in life history parameters of the shorthorn sculpin
Authors: Luksenburg J. A. , Pedersen T.
Published: April 2005

A total of 293 shorthorn sculpins Myoxocephalus scorpius from Tromsø, northern Norway, were sampled between November 1998 and April 1999 to determine sex, total length, age, growth, maturity and mortality. Females grew to larger sizes (L∞=26·9 v. 18·5 cm), matured later (2 v. 1 year of age) at larger size (maturation length=16 v. 14 cm LT), and had lower instantaneous mortality rates (0·93 v. 1·20 year−1) than males. The life history parameters of shorthorn sculpins in northern Norway were more similar to the parameters of short‐lived central European populations than to the parameters of the long‐lived population of Newfoundland. This study confirms that northern Norwegian shorthorn sculpins exhibit sexual dimorphism as in other shorthorn sculpin populations. The relationships between growth pattern, age at maturity and mortality rates observed in the Tromsø population and in other shorthorn sculpin populations, correspond well with the predictions from a published life history model.
Functional significance of the male brood pouch in the reproductive strategies of pipefishes and seahorses: a morphological and ultrastructural comparative study on three anatomically different pouches
Authors: Carcupino M. , Baldacci A. , Mazzini M. , Franzoi P.
Published: April 2005

The morphological organization of the male brood pouch skin of three different species of syngnathids (Nerophis ophidion, Syngnathus abaster and Hippocampus hippocampus), investigated using light and electron microscopy, showed that each pouch had a skin with a different ultrastructure. This reflected different relationships between the paternal body and the developing embryos. In N. ophidion, the bilayered epidermis of the pouch consisted mainly of pavement cells (filament‐containing cells) typical of fish skin. In S. abaster, pavement cells were interspersed with many mitochondria‐rich cells. These cells varied in number during the different functional stages of the pouch and died by apoptosis after the breeding period. Modified secretory ‘flame cone cells’ rich in vesicles and granules characterized the epidermis of H. hippocampus. Although there were specific differences, the vascularized dermis was the only feature common to all three types of pouch. These findings suggest that the brood pouch in Syngnathidae has different functions, which may be related to the different reproductive strategies and ecology of each species.
Neomerinthe bathyperimensis sp. nov. from deep waters of the southern Red Sea
Authors: Zajonz U. , Klausewitz W.
Published: April 2005

A new species of scorpionfish Neomerinthe bathyperimensis is described from a single specimen, dredged in deep waters of the southern Red Sea. The type specimen is aberrant in that it lacks the anal‐fin spines and their supporting pterygiophores. This is the first record of the genus from the Red Sea and the north‐western Indian Ocean.
Relationships between sperm morphometry and sperm motility in the Atlantic salmon
Authors: Gage M. J. G. , Macfarlane C. , Yeates S. , Shackleton R. , Parker G. A.
Published: April 2005

Relationships between spermatozoal design and swimming behaviour were investigated using the significant natural variance in sperm traits in Atlantic salmon Salmo salar. In vitro motility and fertilization experiments were conducted with 86 Atlantic salmon to measure sperm form and function under natural fertilization conditions. Spermatozoal traits of Atlantic salmon showed narrow variance within individuals but differed extensively between samples: mean sperm length varied from 32·3 to 39·5 μm, mean velocity ranged from 18 to 127 μm s−1, and ejaculate longevity varied from 18 to 78 s. In addition to variation in sperm morphometry between fish, a negative relationship was also found between sperm head length and flagellum length. This natural variation in sperm form and function between males is counter‐intuitive since measures are from a single Atlantic salmon population where all males are adapted to a common fertilization environment. No evidence was found that longer sperm, or sperm with longer flagella, achieved faster swimming velocities. Also no evidence was found for a trade‐off between mean sperm velocity and ejaculate longevity. There were significant negative associations, however, between sperm total and flagellum length and ejaculate longevity, so that males with longer sperm had shorter‐lived gametes. This finding has previously been reported in a study across fish species, supporting the theory that increased hydrostatic forces generated by longer flagella may trade against sperm cell longevity.
Fish may fight rather than feed in a novel environment: metabolic rate and feeding motivation in juvenile Atlantic salmon
Authors: Cutts C. J. , Metcalfe N. B. , Taylor A. C.
Published: April 2005

This study tested the hypothesis that juvenile Atlantic salmon Salmo salar with a high resting metabolic rate and probability of dominance will also have a correspondingly higher feeding motivation in a novel environment to offset their greater costs of maintenance. The opposite was found to be the case: Atlantic salmon with a high standard metabolic rate had a slightly but significantly lower feeding motivation. It is hypothesized that Atlantic salmon with higher maintenance costs opt to be more aggressive at the expense of the costly activities associated with feeding, since elevated aggression in a new habitat is a more successful strategy for acquiring a feeding territory (and hence sustaining food intake in the long‐term) than a high feeding motivation alone.
Unusual motility characteristics of sperm of the spotted wolffish
Authors: Kime D. E. , Tveiten H.
Published: April 2005

Unlike the sperm of most teleosts, that of the spotted wolffish Anarhichas minor is motile on stripping, remains motile for at least 2 days and loses motility when exposed to sea water. Computer assisted sperm analysis (CASA) was used to quantitatively examine the motility characteristics of spotted wolffish sperm. Straight line velocity (VSL), beat cross frequency (BCF) and percentage motility were the most sensitive indicators of movement. Sperm trajectories were very different to those of other teleosts examined, showing large side‐to‐side movements of the sperm head and a more ‘wiggly’ behaviour which may be an adaptation to swimming in the viscous gelatinous egg mass. VSL was not altered by pH from 5·0 to 9·0, but was lower at pH 4·5. It was highest at 200 to 500 mOsm and decreased rapidly at <200 mOsm and more slowly at >500 mOsm. It is suggested that the unusual characteristics of spotted wolffish sperm in its trajectory and duration of motility, its release in a fully activated state and its greatly decreased motility in both fresh and sea water are related to a spawning strategy involving mixing of sperm with eggs contained in a gelatinous mass rather than release directly into water in proximity to the ova.
Metabolism of three species of herbivorous loricariid catfishes: influence of size and diet
Authors: Nelson J. A.
Published: April 2005

The questions of whether herbivorous loricariid catfishes are hypometabolic or reduce metabolic demand in response to poor dietary quantity and quality were addressed by comparing resting routine metabolic rates in the presence and absence of different fibre content diets for three loricariid species. Metabolic rates of the three species scaled inter‐specifically as body mass0·736, similar to most other vertebrates. Metabolic rates did not vary with diet quality for two species; one Panaque species had a significantly lower metabolic rate when fed only wood. Comparisons with the literature led to the conclusions that loricariids in general and Panaque in particular do not have unusually low metabolic rates for quiescent catfishes of their size.
A cost‐effective method of preparing larval fish otoliths for reading using enzyme digestion and staining
Authors: Green B. S. , Reilly S. M. , McCormick M. I.
Published: April 2005

A fast and cost‐effective method for examining otoliths in fish larvae was developed whereby the otolith remains in situ. Whole fish of the clownfish Amphiprion melanopus were enzymecleared using a laundry pre‐soak and then stained using the Von Kossa silver staining method for calcium. The otolith nucleus, daily rings and the otolith edge were all clearly visible and were suitable for a variety of age and growth analyses. The total ‘hands on’ time required to process these otoliths was c. 3 min, and multiple samples could be processed simultaneously. The reduction in labour of this method to produce clear daily rings in the otolith lends itself to broad use in fish biology where large quantities of otoliths need to be examined in a cost‐ and time‐efficient manner.
Transient changes in behaviour lead to heroin overdose: results from a case‐crossover study of non‐fatal overdose
Authors: Dietze Paul , Jolley Damien , Fry Craig , Bammer Gabriele
Published: April 2005

Background and aims  Heroin overdose is a serious consequence of heroin use and one of the leading causes of premature death and illness in Australia. Despite considerable research effort little is known about the effects of transient changes in heroin user behaviour and the links to overdose. This research is the first to use a suitable methodology to allow such ephemeral changes and their effects on non‐fatal heroin overdose to be examined.

Methods  A case‐crossover design was used in which non‐fatal heroin overdose survivors’ recall of risk behaviours in the 12 hours prior to overdose (hazard period) was compared to their recall of risk behaviours in the 12 hours prior to a selected non‐overdose heroin injection (control period).

Results  A total of 155 participants were able to provide valid details of hazard and control periods. A dose–response relationship was observed between the self‐reported amount of heroin used and likelihood of overdose (e.g. > AUD50, OR 12.97, 95% CI 2.54–66.31). The use of benzodiazepines (OR 28, 95% CI 3.81–205.79) or alcohol (OR 2.88, 95% CI 1.29–6.43), during the hazard period was related to overdose risk, but the effect of alcohol was attenuated by the effect of benzodiazepines. Shifting from private to public locations between control and hazard periods was also related to increased risk of overdose (OR 3.63, 95% CI 1.66–7.93).

Conclusions  We demonstrate the value of a new methodology to explore heroin overdose, as well as discussing its limitations and ways to overcome them in future. In terms of our findings, overdose prevention messages need to highlight the impact of these transient changes in behaviour and to emphasize the risks of using higher doses of heroin as well as continuing to emphasize the risks of combining heroin with other central nervous system (CNS) depressants. Safer environments for heroin use, such as injecting rooms, may also reduce the chances of overdose.