bluuebunny/crossref_metadata_2025 huggingface dataset:
A Design Approach for the Systematic Improvement of Support Locations for Vibrating Circuit Cards
Authors: Pitarresi J. M. , Di Edwardo A. V.
Published: April 2008

This paper approaches the problem of improving an initial guess at support locations for a vibrating circuit card so as to increase the first natural frequency of the card. The finite element method and structural dynamic modification techniques are combined with a simple sequential search algorithm to systematically improve the location of point supports for a circuit card populated with components. It is found that the proposed methodology can be useful for determining the support locations of a circuit card so as to increase its fundamental natural frequency. A case study is presented in which the original support locations on an existing commercial power supply circuit card are systematically improved giving a better than two fold increase in the natural frequency. Additionally, finite element modeling approaches for determining the modal characteristics of a circuit card are compared with experimental results.
Subcooled Pool Boiling Critical Heat Flux in Dielectric Liquid Mixtures
Authors: Lee T. Y. Tom , Mahalingam Mali , Normington Peter J. C.
Published: April 2008

The beneficial effect of using dielectric liquid mixture in reducing temperature overshoot in pool boiling has been studied by the authors (Normington et al., 1992). The current experimental work addresses the influence of mixtures of dielectric liquids on the critical heat flux (CHF) in pool boiling. Two families of dielectric liquids were evaluated: perfluorocarbon liquids and perfluoropolyether liquids. Each set of the family consisted of two liquids with boiling points ranging from 80°C−110°C. Both 100 percent of each liquid and mixtures of two liquids were tested. Video filming was used along with electronic data collection. The perfluoropolyether liquids showed an increase in CHF as more high boiling liquid was added to the mixture, while the perfluorocarbon liquids had a constant CHF for all mixtures.
Computer Simulation of Thermo-Mechanical Fatigue of Solder Joints Including Microstructure Coarsening
Authors: Hacke P. , Sprecher A. F. , Conrad H.
Published: April 2008

Thermo-mechanical cycling (– 30°/130°C) tests were performed on 63Sn37Pb solder joints with cycle periods of 12–48 min. The effect of phase (grain) size was incorporated into the integrated matrix creep damage concept to take into account the coarsening which occurred during the thermal cycling. It was thereby determined that failure (50 percent load drop) results at a total integrated matrix plastic strain (creep) of 1.39 and that the measured fatigue life is only 21 percent of that predicted assuming no coarsening. The coarsening during the thermo-mechanical cycling was in reasonable accord with the cubic coarsening law. However, it was more rapid than occurred during isothermal aging at zero stress.
Coating of Electronic Components by the RTV Dispersion—Part II: Determination of the Residual Yield Stress After Deposition, and Method to Produce a Drop of Required Cured Skin Thickness and Diameter
Authors: Owczarek J. A.
Published: April 2008

In this part of the paper the drop test method is used to show that RTV dispersions are in fact plastic “false body” materials, and to determine the magnitudes of the residual yield stresses after shearing for different RTV dispersion lots. With the aid of the equation for the wall shear stress derived in Part I of this paper [1], a correlation equation between the residual yield stress and the deposition variables is obtained, and analysis is made of the drop spreading phenomenon. It is shown that the drop spread, which is responsible for the run-over, or wicking, of external leads of electronic circuits, can be decreased by decreasing the deposition rate of the encapsulant. Finally, a method is developed to determine the required deposition flow rate and deposition time to produce a drop having required final diameter and cured skin thickness.
An Integral Heat Sink for Cooling Microelectronic Components
Authors: Bhavnani S. H. , Tsai C.-P. , Jaeger R. C. , Eison D. L.
Published: April 2008

Liquid immersion cooling is rapidly becoming the mechanism of choice for the newest generation of supercomputers. Miniaturization at both the chip and module level places a severe constraint on the size of the heat sink employed to dissipate the high heat fluxes generated. A study was conducted to develop a surface that could augment boiling heat transfer from silicon surfaces under these constraints. The surface created consists of reversed pyramidal features etched directly on to the silicon surface. Experiments were conducted in a saturated pool of refrigerant-113 at atmospheric pressure. The inexpensive crystallographic etching techniques used to create the enhanced features are described in the paper. The main characteristics of interest in the present study were the incipient boiling superheat and the magnitude of the temperature overshoot at boiling incipience. Results were obtained for test sections with various cavity densities, and compared with data for the smooth untreated surface. It was found that incipient boiling superheat was reduced from a range of 27.0–53.0° C for the untreated silicon surface, to a range of 2.5–15.0° C for the enhanced surfaces. The overshoot also decreased considerably; from about 12.0–18.0° C for two classes of untreated surfaces, to a range of 1.5–5.3° C for the enhanced surfaces. The values of the incipient boiling superheat, and those of the overshoot decreased with a decrease in cavity mouth size. Two ratios of heat source surface area to the area of the enhanced surface were studied. The overshoot values obtained for these surfaces were compared with those observed for some commonly used enhanced surfaces. An elementary numerical study was conducted to estimate the magnitude of heat spreading.
A Simplified Thermal Analysis and Design Methodology for Printed Circuit Boards
Authors: Hadim A.
Published: April 2008

A simplified methodology is developed for thermal analysis and design of printed circuit boards. It combines the use of computer-aided thermal network modeling and a simplified experimental technique. In order to demonstrate its capabilities, this methodology is implemented to correlate natural convection on a printed circuit board oriented horizontally inside an enclosure. The empirical constants used in the correlation were determined through a numerical algorithm in which the sum of the squared error between calculated temperatures and experimental measurements is minimized using the downhill simplex algorithm.
Forced Convective Cooling Enhancement of Electronic Package Configurations Through Self-Sustained Oscillatory Flows
Authors: Nigen J. S. , Amon C. H.
Published: April 2008

Two-dimensional arrangements of electronic packages surface mounted to a printed circuit board represent grooved-channel geometries. For a certain range of Reynolds numbers, these geometries excite and sustain instabilities that are normally damped in planar Poiseuille flows. This results in a bifurcation to a self-sustained oscillatory state, which improves mixing and thereby enhances convective heat transport. Numerical simulations of the flow field and heat transfer characteristics of oscillatory and nonoscillatory flows for five grooved channels are presented. Additionally, the numerically obtained flow field corresponding to a suspended electronic package is analyzed. The extent of heat transfer enhancement is gauged through direct comparison to results corresponding to the steady-flow regime. Local heat transfer coefficients are determined and used to calculate the temperature distribution within a surface-mounted package. Moreover, the importance of using locally-defined instead of spatially-averaged heat transfer coefficients for thermal design and analysis of electronic packages is discussed.
Changes in the Plasmodial Surface Anion Channel Reduce Leupeptin Uptake and Can Confer Drug Resistance in
Plasmodium falciparum
-Infected Erythrocytes
Authors: Lisk Godfrey , Pain Margaret , Gluzman Ilya Y. , Kambhampati Shivkumar , Furuya Tetsuya , Su Xin-zhuan , Fay Michael P. , Goldberg Daniel E. , Desai Sanjay A.
Published: April 2008

Cysteine protease inhibitors kill malaria parasites and are being pursued for development as antimalarial agents. Because they have multiple targets within bloodstream-stage parasites, workers have assumed that resistance to these inhibitors would not be acquired easily. In the present study, we used in vitro selection to generate a parasite resistant to growth inhibition by leupeptin, a broad-profile cysteine and serine protease inhibitor. Resistance was not associated with upregulation of cysteine protease activity, reduced leupeptin sensitivity of this activity, or expression level changes for putative cysteine or serine proteases in the parasite genome. Instead, it was associated with marked changes in the plasmodial surface anion channel (PSAC), an ion channel on infected erythrocytes that functions in nutrient and bulky organic solute uptake. Osmotic fragility measurements, electrophysiological recordings, and leupeptin uptake studies revealed selective reductions in organic solute permeability via PSAC, altered single-channel gating, and reduced inhibitor affinity. These changes yielded significantly reduced leupeptin uptake and could fully account for the acquired resistance. PSAC represents a novel route for the uptake of bulky hydrophilic compounds acting against intraerythrocytic parasite targets. Drug development based on such compounds should proceed cautiously in light of possible resistance development though the selection of PSAC mutants.
Trypanocidal and Leishmanicidal Activities of Sesquiterpene Lactones from
Ambrosia tenuifolia
Sprengel (Asteraceae)
Authors: Sülsen Valeria P. , Frank Fernanda M. , Cazorla Silvia I. , Anesini Claudia A. , Malchiodi Emilio L. , Freixa Blanca , Vila Roser , Muschietti Liliana V. , Martino Virginia S.
Published: April 2008

Bioassay-guided fractionation of the organic extract of
Ambrosia tenuifolia
Sprengel (Asteraceae) led to the isolation of two bioactive sesquiterpene lactones with significant trypanocidal and leishmanicidal activities. By spectroscopic methods (
1
H- and
13
C-nuclear magnetic resonance, distortionless enhancement by polarization transfer, correlated spectroscopy, heteronuclear multiple-quantum coherence, electron impact-mass spectrometry, and infrared spectroscopy), these compounds were identified as psilostachyin and peruvin. Both compounds showed a marked in vitro trypanocidal activity against
Trypanosoma cruzi
epimastigotes with 50% inhibitory concentration (IC
50
) values of less than 2 μg/ml. Psilostachyin exerted a significant in vitro activity against the trypomastigote forms of
T. cruzi
(IC
50
, 0.76 μg/ml) and was selected for in vivo testing. Psilostachyin-treated mice had a survival of 100% and lower parasitemia values than control mice. Both compounds were also tested on
Leishmania
sp. promastigotes: psilostachyin (IC
50
, 0.12 μg/ml) and peruvin (IC
50
, 0.39 μg/ml) exerted significant leishmanicidal activities. This is the first time that the trypanocidal and leishmanicidal activities of these compounds have been reported. The selectivity index (SI) was employed to evaluate the cytotoxic effect of lactones on T lymphocytes. Although the SIs of both compounds were high for
T. cruzi
epimastigotes, psilostachyin was more selective against trypomastigotes (SI, 33.8) while peruvin showed no specificity for this parasite. Both compounds presented high selectivity for
Leishmania
spp. The results shown herein suggest that psilostachyin and peruvin could be considered potential candidates for the development of new antiprotozoal agents against Chagas' disease and leishmaniasis.
In Vitro Evaluation of CBR-2092, a Novel Rifamycin-Quinolone Hybrid Antibiotic: Microbiology Profiling Studies with Staphylococci and Streptococci
Authors: Robertson Gregory T. , Bonventre Eric J. , Doyle Timothy B. , Du Qun , Duncan Leonard , Morris Timothy W. , Roche Eric D. , Yan Dalai , Lynch A. Simon
Published: April 2008

We present data from antimicrobial assays performed in vitro that pertain to the potential clinical utility of a novel rifamycin-quinolone hybrid antibiotic, CBR-2092, for the treatment of infections mediated by gram-positive cocci. The MIC
90
s for CBR-2092 against 300 clinical isolates of staphylococci and streptococci ranged from 0.008 to 0.5 μg/ml. Against
Staphylococcus aureus
, CBR-2092 exhibited prolonged postantibiotic effects (PAEs) and sub-MIC effects (SMEs), with values of 3.2, 6.5, and >8.5 h determined for the PAE (3× MIC), SME (0.12× MIC), and PAE-SME (3× MIC/0.12× MIC) periods, respectively. Studies of genetically defined mutants of
S. aureus
indicate that CBR-2092 is not a substrate for the NorA or MepA efflux pumps. In minimal bactericidal concentration and time-kill studies, CBR-2092 exhibited bactericidal activity against staphylococci that was retained against rifampin- or intermediate quinolone-resistant strains, with apparent paradoxical cidal characteristics against rifampin-resistant strains. In spontaneous resistance studies, CBR-2092 exhibited activity consistent with balanced contributions from its composite pharmacophores, with a mutant prevention concentration of 0.12 μg/ml and a resistance frequency of <10
−12
determined at 1 μg/ml in agar for
S. aureus
. Similarly, CBR-2092 suppressed the emergence of preexisting rifamycin resistance in time-kill studies undertaken at a high cell density. In studies of the intracellular killing of
S. aureus
, CBR-2092 exhibited prolonged bactericidal activity that was superior to the activities of moxifloxacin, rifampin, and a cocktail of moxifloxacin and rifampin. Overall, CBR-2092 exhibited promising activity in a range of antimicrobial assays performed in vitro that pertain to properties relevant to the effective treatment of serious infections mediated by gram-positive cocci.
Use of Gene Dosage Effects for a Whole-Genome Screen To Identify
Mycobacterium marinum
Macrophage Infection Loci
Authors: Park Bonggoo , Subbian Selvakumar , El-Etr Sahar H. , Cirillo Suat L. G. , Cirillo Jeffrey D.
Published: April 2008

We recently identified two loci,
mel1
and
mel2
, that affect macrophage infection by
Mycobacterium marinum
. The ability of these loci to confer enhanced infection in trans is presumably due to gene dosage effects since their presence on plasmids increases expression from five- to eightfold. Reasoning that this phenomenon would allow identification of other mycobacterial genes involved in macrophage infection, we conducted a screen of an
M. marinum
DNA library that provides 2.6-fold coverage of the entire genome for clones that affect macrophage infection. Our preliminary screen identified 76 plasmids that carry loci affecting macrophage infection. We eliminated plasmids that do not confer the expected phenotype when retransformed (70%), that have identical physical maps (5%), or that carry either of the
mel1
or
mel2
loci (14%) from further consideration. Four loci that confer enhanced infection (
mel
) and four that confer repressed infection (
mrl
) of macrophages were identified, and two of each group were chosen for detailed analysis. Saturating transposon mutagenesis was used to identify the loci responsible, and
M. marinum
mutants were constructed in the genes involved. We expect these genes to provide insight into how mycobacteria parasitize macrophages, an important component of innate immunity.
The Active-Site Cysteinyls and Hydrophobic Cavity Residues of ResA Are Important for CytochromecMaturation inBacillus subtilis
Authors: Hodson Christopher T. C. , Lewin Allison , Hederstedt Lars , Le Brun Nick E.
Published: May 2008

ResA is an extracytoplasmic membrane-bound thiol-disulfide oxidoreductase required for cytochromecmaturation inBacillus subtilis. Previous biochemical and structural studies have revealed that the active-site cysteinyls cycle between oxidized and reduced states with a low reduction potential and that, upon reduction, a hydrophobic cavity forms close to the active site. Here we report in vivo studies of ResA-deficientB. subtiliscomplemented with a series of ResA variants. Using a range of methods to analyze the cellular cytochromeccontent, we demonstrated (i) that the N-terminal transmembrane segment of ResA serves principally to anchor the protein to the cytoplasmic membrane but also plays a role in mediating the activity of the protein; (ii) that the active-site cysteines are important for cytochromecmaturation activity; (iii) that Pro141, which forms part of the hydrophobic cavity and which adopts acisconformation, plays an important role in protein stability; (iv) that Glu80, which lies at the base of the hydrophobic cavity, is important for cytochromecmaturation activity; and, finally, (v) that Pro141 and Glu80 ResA mutant variants promote selective maturation of low levels of onec-type cytochrome, subunit II of the cytochromecoxidasecaa3, indicating that this apocytochrome is distinct from the other three endogenousc-type cytochromes ofB. subtilis.
Population ecology ofCirsium pitcherion Lake Huron sand dunes: II. Survivorship of plants
Authors: D'Ulisse Angelo , Maun M. A.
Published: May 2008

Cirsium pitcheri is a threatened plant species endemic to the shoreline sand dunes of the Greak Lakes. In this study, we attempted to identify some of the environmental factors that may limit the growth, survival, and reproduction of its populations. This species occurs as a minor associate among mixed populations of three dominant grass species, Ammophila breviligulata, Calamovilfa longifolia, and Andropogon scoparius in sandy soil of varying texture (fine, medium, coarse, or shingle). It occupies bare areas within stands of grasses on the first and second sand dune ridges and is prevalent in blowouts. The size class distribution based on the number of leaves per plant showed that the population was dominated by young plants (1–5 leaves) and the relative frequency of juveniles in each successive size class decreased from the smallest to the largest size class. Large juveniles were few in number, which suggests that there was high mortality during the juvenile phase. Seedling mortality in individual plots ranged from 11 to 90% in 1993 and 0 to 70% in 1994. Seed production of its populations was severely reduced because of consumption of whole capitula by white-tailed deer. Transition probabilities indicated that the probability of flowering was dependent on the size of the plant based on the longest leaf length. Keywords: survivorship, deer grazing, transition probability, sand texture, Cirsium pitcheri.
Soil–pile–cap static interaction analysis by finite and infinite elements
Authors: Liu Weiming , Novak Milos
Published: May 2008

A direct analysis of pile–soil static interaction by the combination of finite and infinite elements is presented. The pile and the near-field soil medium are modelled by finite elements, whereas the far-field soil medium is modelled by mapped infinite elements. Axially loaded single piles and single piles with caps subject to monotonic loading are investigated. The soil is assumed to be either elastic or elastic–perfect plastic. A weak zone is introduced around the pile to approximately account for slip between the soil and the pile. Numerical results show that this approach is quite efficient and versatile for various soil–structure interaction problems. Key words: pile, soil, cap, elastoplasticity, finite element, infinite element.
Subsidence owing to tunnelling. II. Evaluation of a prediction technique
Authors: Rowe R. Kerry , Lee K.M.
Published: May 2008

A numerical and a simplified empirical design procedure (based on the concept of the gap parameter) for predicting settlement above tunnels constructed in soft ground are evaluated with reference to 14 case histories. These records encompass very stiff to soft clays. A comparison of observed and calculated behaviour indicates that the proposed numerical and empirical approaches are capable of providing a reasonable estimate of the gap and the surface settlement provided that the soil parameters are reliably determined. It is suggested that the simplified procedure may be used for preliminary design. The gap parameter can also be used in conjunction with more sophisticated numerical methods to predict the variation in settlement with position and depth at critical sections of the tunnelling project. Key words : tunnelling, settlement, subsidence, clays, soft-ground analysis, design, case history, finite element.
Competition between Calamagrostiscanadensis and Epilobiumangustifolium under different soil temperature and nutrient regimes
Authors: Landhäusser Simon M. , Lieffers Victor J.
Published: May 2008

The relative competitive abilities of Calamagrostiscanadensis (Michx.) Beauv. and Epilobiumangustifolium L. were tested in two sets of replacement series experiments. Both species were grown in monocultures and a range of mixtures in 25-cm pots. In the first set, substrates were held at either 9 or 21 °C; in the second set the pots were fertilized at high or low rates. In the 21 °C treatment C. canadensis was more competitive than E. angustifolium (relative crowding coefficient for C. canadensis towards E. angustifolium was 2.88), while there were little competition differences in the cool soil conditions. Under the cool soil temperatures, however, E. angustifolium showed higher vegetative reproduction than under the warm soil conditions. In the high nutrient conditions, C. canadensis was more competitive than E. angustifolium (relative crowding coefficient for C. canadensis towards E. angustifolium was 5.84). There was little competition in the low nutrient experiment. These experiments indicate that if both species colonize a site simultaneously, C. canadensis will outcompete E. angustifolium under most conditions, as suggested from field observations of earlier researchers.
Functional histology of quill erection in the porcupine, Erethizon dorsatum
Authors: Chapman David M. , Roze Uldis
Published: April 2008

The histology of the porcupine's skin and subcutis is described. The functional relationships of the thoracic skin during elevation of the quills involve a smooth arrector muscle attached to quill sets, one set behind the other, with the muscle at a slant usually from a single root tip of one set to the distal part of the follicles in the caudal set. Stretched elastin returns the quills to their resting position. There is a low-resistance pathway for the tilting quill roots through loose connective tissue and fat until a collagenous strand attached to the quill set stops further tilt. The lumbosacral region (rosette) has a two-layered arrector, but it attaches to only its own quill set and inserts into the dermis. Both regions have a varied and complicated system of transverse and oblique muscles associated with the roots in a set. (The occurrence of obliques is variable in the thoracic region.) A hypothesis is presented concerning the mechanism of quill detachment from the porcupine after the quill is rammed into a predator. This involves the shearing of the conical root tip along its adherent follicular cells and a stopping device (spool) to prevent the root from self-stabbing.
Morphological and genetic differentiation of 11 populations of the African catfishChrysichthys nigrodigitatus(Siluroidei; Claroteidae), with consideration of their biogeography
Authors: Adépo-Gourène Béatrice , Agnèse Jean-François , Teugels Guy G. , Risch Luc M. , Hanssens Mark M.
Published: April 2008

Eleven samples of Chrysichthys nigrodigitatus and one sample of C. maurus were studied using morphometrics and enzyme polymorphism. Samples from opposite areas in the range of the species were most differentiated morphologically (Dagana in Senegal and Selingue in Mali, on one hand, and Bas Kouilou in Congo, on the other hand). In the sample from Bas Kouilou, most specimens overlap those from Ebrie Lagoon in Côte d'Ivoire. The populations from Côte d'Ivoire are genetically the most variable and have the highest number of alleles in common with the sample of C. maurus (ancestral alleles). The samples from the limits of the species' range (Dagana, Bas Kouilou) are those that have the least polymorphism (both monomorphs) and the fewest alleles in common with C. maurus. On the basis of these results we present a hypothetical scenario for the colonization of basins by populations of C. nigrodigitatus after the last glaciation. Colonization started in the area between Côte d'Ivoire and Benin. From this region of origin, some populations colonized the basins to the west via the coastal area up to Senegal. Independently, other populations colonized the basins to the east via the coastal area up to Zaïre. The colonization of the Niger most likely occurred through its Lower Delta.
Effects of salt on the growth and timing of reproduction of the deer mouse (Peromyscus maniculatus borealis)
Authors: Woolfenden Bonnie E. , Millar John S.
Published: April 2008

The effects of salt on the growth and timing of reproduction in Peromyscus maniculatus borealis were investigated in the laboratory, as well as in the Kananaskis Valley, Alberta, Canada, to test the hypothesis that sodium limitation results in delayed maturation of young animals. Laboratory-born juveniles were assigned to treatment groups in which the mother received nutritionally complete food (control) or sodium-deficient food during the preweaning period. Growth of male nestlings was not affected by sodium deficiency, but among female nestlings, growth was slower in sodium-deficient groups than in controls. Juveniles were also assigned to one of two postweaning diet groups at weaning, resulting in four treatment groups based on the diet received during the pre- and post-weaning periods. For both sexes, the overall growth rate was higher in animals given nutritionally complete food in both the pre- and post-weaning period than in animals given sodium-deficient food during the postweaning period. Salt supplementation in the field resulted in the birth of significantly more litters to overwintered females than to nonsupplemented controls, but not did not result in a greater number of young weaned from each litter. Salt supplementation did not affect initiation of breeding or length of the breeding season for overwintered females, and did not affect overall growth rates or initiation of reproduction in young-of-the-year mice. Mice appear to obtain sufficient salt from their natural diets.
The fate of14C infused into the swim bladder of the American eel,Anguilla rostrata
Authors: Pelster B. , Bailey J. R. , Driedzic W. R.
Published: April 2008

The present study analyses the capability of swim-bladder tissue of the American eel (Anguilla rostrata) to incorporate either intermediates of glucose metabolism or blood-borne fatty acids into the swim-bladder lipid fraction. At 29.9 ± 6.0 nmol∙min−1∙g−1wet mass, the activity of acyl-CoA synthetase was about 10-fold higher than the activity of acetyl-CoA carboxylase, a key enzyme required for de novo fatty acid synthesis. The level of fatty acid synthase activity was too low to be detected by the enzymatic test used. When the swim bladder was perfused for 1 h with medium containing 5 mmol∙L−1glucose as the only fuel, 11.5 ± 3.3 nmol glucose∙g−1tissue was incorporated into the lipid pool. When, in addition to 5 mmol∙L−1glucose, 1.1 mmol∙L−1acetate was added to the perfusate, incorporation of acetate into the lipid pool was 3.06 ± 1.14 nmol acetate∙g−1tissue. When 0.41 mmol∙L−1palmitate was added to the glucose-containing perfusate, 144.5 ± 24.2 nmol palmitate∙g−1tissue was incorporated into the lipid pool. These results demonstrate that de novo synthesis of lipids in swim-bladder tissue is only possible at a very low rate and cannot explain the difference in numbers of carbon atoms entering and leaving the swim-bladder wall. Blood-borne fatty acids, however, can be readily taken up and incorporated into swim-bladder lipids.
Postnatal growth and allometry of harbour porpoises from the Bay of Fundy
Authors: Read Andrew J. , Tolley Krystal A.
Published: April 2008

We described patterns of growth and allometry from observations of 203 female and 198 male harbour porpoises, Phocoena phocoena, killed in commercial fisheries in the Bay of Fundy between 1985 and 1993. Gompertz growth curves were used to predict length, mass, and girth at physical maturity. Asymptotic sizes and growth rates were greater in females for all three characters. The pattern of allometry was consistent between sexes, but varied according to body region. The characters in the head and thoracic regions exhibited negative allometry, but those in the posterior of the body were isometric. Most characters showed the same growth rates for the two sexes, except those in the thoracic region, for which females exhibited faster growth than males. These results are consistent with those of several other studies of the harbour porpoise in which faster growth and larger sizes are attained by females.
Physiological responses by lagomorphs to resource limitations imposed by habitat fragmentation: implications for condition-sensitive predation
Authors: Villafuerte R. , Litvaitis J. A. , Smith D. F.
Published: April 2008

Human land uses have resulted in landscape mosaics with habitat patches that vary in quality. Patch quality (including the abundance of food and the risk of predation) can affect the survival of animals that are sequestered in remnant patches of habitat. Recent investigations of the demography of New England cottontails (Sylvilagus transitionalis) have shown that cottontails on small (resource poor) patches were in poor physical condition (based on body mass) and often foraged at sites with limited cover. This resulted in a higher mortality rate than among rabbits occupying large (resource rich) patches. To gain additional insight into the consequences of habitat fragmentation, we tracked the physiological condition of rabbits occupying small and large patches during winter. The physiological condition of rabbits was determined using the urinary urea nitrogen:creatinine ratio, and the results were compared with similar indices obtained from captive rabbits. Consistent with our expectations, the nitrogen:creatinine ratios indicated that rabbits on small patches were nutrient limited for a longer period than rabbits on large patches. Transmitter-equipped rabbits on small patches had a lower survival rate and died earlier than rabbits on large patches. All mortalities were predator related. Using these data, we developed a simple model that supports the role of "condition-sensitive predation" as a major factor limiting populations of New England cottontails. Our results also demonstrate the utility of sampling physiological condition to provide an index of quality of lagomorph habitat in human-dominated landscapes.
Survival of fledgling Ferruginous Hawks in northern Montana
Authors: Zelenak James R. , Rotella Jay J. , Harmata Alan R.
Published: April 2008

Few data exist regarding survival of Ferruginous Hawks (Buteo regalis) during the fledgling period. Consequently, we estimated the survival rate of juvenile Ferruginous Hawks from fledging to dispersal from the breeding area in northern Montana in 1993 – 1994 using radiotelemetry. A 171-km2 study area contained 24 occupied breeding sites in both years (7.12 km2/pair). Mean productivity was 0.96 young fledged per occupied breeding site (SE = 0.19, n = 48) and 2.30 young fledged per successful nest (SE = 0.21, n = 20). The average fledging age was 43.3 days. The survival rate for 27 radio-marked fledglings was high during the 3 weeks after fledging (Ŝ = 0.86, SE = 0.02). No fledgling mortality occurred > 10 days after fledging. When fledgling mortality was considered, occupied breeding sites produced an average of 0.82 dispersing young (SE = 0.24) and successful nests produced an average of 1.96 dispersing young (SE = 0.18). Our data concur with smaller data sets from earlier studies, which suggested that postfledging mortality is low.
A comment on the age at onset of breeding of male Weddell seals (Leptonychotes weddellii)
Authors: Testa J. Ward
Published: April 2008

In an otherwise valuable contribution, Bartsh et al. (S.S. Bartsh, S.D. Johnston, and D.B. Siniff. 1992. Can. J. Zool. 70: 680 – 692) reached the conclusion that the youngest age at which male Weddell seals (Leptonychotes weddellii) become sexually active in their breeding colonies was 7 years, with first breeding likely, on average, in year 8. While plausible, this conclusion was based on only 5 seals of known age and 9 seals whose age was estimated from a length – age regression model. In addition to methodological problems with the regression model used by Bartsh et al., its application to a sample of known-age male Weddell seals correctly predicted the ages of only 25% of seals in the range of ages likely to include the age at social maturity, and was commonly off by 3 – 5 years and more. The age at onset of sexual activity of male Weddell seals cannot be determined from that analysis.
The structure of the antennal heart ofAedes aegypti(Linnaeus)
Authors: Sun B. D. , Schmidt J. M.
Published: April 2008

The structure of the antennal heart of Aedes aegypti (L.) (Diptera: Culicidae) was observed using light and electron microscopy. The antennal heart consists of several distinct regions including a single layer of columnar cells, the chamber walls, the valve, the z-body, the muscle fibres, and the connective tissue filaments. The columnar cells are structurally similar to secretory and osmoregulatory cells. Features of tendinous epidermal cells typically involved in the attachment of muscles to the cuticle can be observed in various areas of the antennal heart when it is examined as a whole. A model describing the pumping mechanism of the antennal heart in A. aegypti is presented.
An old problem in a new perspective: the enigmatic evolutionary relationships of some Australian freshwater planarians (Platyhelminthes, Tricladida, Paludicola)
Authors: Sluys Ronald
Published: April 2008

This study addresses the uncertain phyletic status of four Australian freshwater planarians: Dugesia glandulosa (Kenk, 1930), Planaria graffi Weiss, 1909, P. hoernesi Weiss, 1909, P. boehmigi Weiss, 1909. Planaria hoernesi and P. boehmigi are redescribed on the basis of newly prepared type material. Following up on previous studies, a new phylogenetic hypothesis concerning relationships within the family Dugesiidae is developed. In view of this hypothesis, and taking into account the incomplete information on the species' morphology, it is concluded that P. graffi is best assigned to the genus Cura Strand, 1942. Reinterpretation of features in species of the current genus Romankenkius Ball, 1974 resulted in a redefinition of this genus. It is shown that in its new concept, the genus Romankenkius accommodates the species R. bilineatus Ball &Tran, 1979, R. boehmigi (Weiss, 1909), R. hoernesi (Weiss, 1909), R. glandulosus (Kenk, 1930), R. kenki Ball, 1974, R. libidinosus Sluys &Rohde, 1991, R. michaelseni (Böhmig, 1902), R. pedderensis Ball, 1974, and R. patagonicus (Borelli, 1901). The current genus Cura is restricted to the species C. pinguis (Weiss, 1909), C. foremanii (Girard, 1852), and C. graffi (Weiss, 1909).
Glochidial metamorphosis of the freshwater mussel Lampsilis cardium (Bivalvia: Unionidae) on larval tiger salamanders, Ambystoma tigrinum ssp. (Amphibia: Ambystomidae)
Authors: Watters G. Thomas
Published: April 2008

Larval tiger salamanders (Ambystoma tigrinum ssp.) were infected with glochidia of the freshwater mussel Lampsilis cardium in laboratory experiments. At 20–21 °C, metamorphosis occurred from 9 to 39 days, primarily between 9 and 17 days. The percentage of attached glochidia that metamorphosed varied from 0.27 to 15.7%. Metamorphosis on the salamanders occurred more quickly than on a known piscine host, largemouth bass (Micropterus salmoides), but a smaller percentage of the total attached glochidia metamorphosed. The role of amphibians as hosts of freshwater mussels in North America has not been addressed. Recognizing such a relationship could have important consequences for our understanding of mussel zoogeography.
Food-chain chemistry, reproductive success, and foraging behaviour of songbirds in acidified maple forests of central Ontario
Authors: Mahony Nancy , Nol Erica , Hutchinson Tom
Published: April 2008

We examined the breeding success of two insectivorous bird species, the resident black-capped chickadee (Parus atricapillus) and the Neotropical migrant chestnut-sided warbler (Dendroica pensylvanica), in relation to food-chain chemistry at a healthy and a declining forest site in central Ontario, Canada. The health of sugar maples (Acer saccharum) was poorer and the pH of both soil and throughfall was lower at the declining site than at the healthy site. The calcium and magnesium concentrations and the calcium:aluminum ratio in the soil were also lower at the declining site than at the healthy site. The calcium, magnesium, and phosphorus concentrations and the calcium:aluminum ratio in sugar maple foliage were lower at the declining site than at the healthy site, indicating extensive acid leaching of the soil and foliage at the declining site. Caterpillars (Geometridae) at the declining site had a lower calcium concentration and beetles had a lower magnesium concentration than these groups at the healthy site. The calcium:aluminum ratios in the tissues of insects in both groups were lower at the declining site than at the healthy site, paralleling the foliar and soil chemical differences. There were, however, no differences in clutch or brood sizes, or percent hatch, for either bird species between the healthy and declining sites. Chickadees consistently foraged lower in the canopy at the declining site, a possible compensatory behaviourial response to canopy dieback and (or) lower food quality in the upper canopy.
The role of phylogeny and behavioral competition in the evolution of coexistence among primates
Authors: Houle Alain
Published: April 2008

No analysis of coexistence among primates has ever considered phylogenetic distances and behavioral competition. The present model proposes that high levels of behavioral competition strongly incite divergence of the respective positions of sympatric species in niches, especially when these species are closely related. This divergence is then reflected in the morphologies of coexisting species (individuals exploit new dimensions of niches and their associated morphologies are selected for) and consequently in their phylogenetic distances. Sister species (defined here as those from the same subgenus or same species group) are phylogenetically closer than kin species (of the same genus but different subgenera or species groups). Accordingly, if a minimum phylogenetic distance is a condition of stable coexistence, then kin (and higher ranking) species, but not sister species, are expected to coexist in ecological communities. Moreover, the intensity of behavioral competition among coexisting species should be inversely proportional to phylogenetic distance. (Taxa are said to have high levels of behavioral competition if they display high rates of aggressive behaviors and simultaneous low rates of grooming behaviors.) To test these hypotheses, 41 ecological communities were reviewed. The conclusions are that (i) primate sister species do coexist, but very exceptionally compared with kin species (Wilcoxon's signed ranks test, p < 0.0001), suggesting that coexistence is possible provided a minimum phylogenetic distance is respected; (ii) there is a negative relationship between taxonomic distance and the rate of aggression among sympatric primates (p = 0.04) and a positive relationship between this distance and the rate of interspecific grooming behaviors (p = 0.028), supporting the hypothesis that stable coexistence is possible if sympatric species reduce and maintain low levels of behavioral competition.
Courtship, copulation, and genital mechanics in Physocyclus globosus (Araneae, Pholcidae)
Authors: Huber Bernhard A. , Eberhard William G.
Published: April 2008

The pholcid spider Physocyclus globosus (Taczanowski, 1873) was observed and videotaped courting and copulating, and genital mechanics and movements were analyzed by serial sectioning of freeze-fixed pairs. Just prior to copulation, the chelicerae of the male engage an apophysis on the female's epigynum. During copulation the male vibrates his abdomen rhythmically and makes repeated, relatively stereotyped twisting and flexing movements with his pedipalps, which are inserted simultaneously but asymmetrically in the female. The palps squeeze the female in the area of her epigyneal plate. Copulation with non-virgin females results in the extrusion of a mass of sperm from the female's genitalia during copulation or up to several minutes after it ends; no such masses result from copulations with virgin females. Sperm extrusion was not associated consistently with precedence of sperm from either the first or the second male. It is argued that the palpal movements, and perhaps most rhythmic genitalic movements, in spiders may best be interpreted as a result of sexual selection by means of cryptic female choice, and probably function to provide females with additional information about the male. Pholcids in general, and some genera in particular (including Physocyclus), may be unusual in that the vigour of males may play a significant role during copulatory courtship, as their palps have massive muscles that are only used during copulation.
The influence of sex and reproductive state on diet preference in four terrestrial mammals of the French Guianan rain forest
Authors: Henry O.
Published: April 2008

The diets of males and pregnant and nonpregnant females were studied in four French Guianan mammal species, three rodents and one artiodactyl, illustrating a gradient of size, mass, and gestation, and thus of energy and protein requirements. In the rodents (Oryzomys capito, Proechimys cuvieri, Dasyprocta leporina), males were more frugivorous than females, whereas the reverse was the case in the artiodactyl (Tayassu tajacu). For all species, males ate the most pulp, while pregnant females focused on seeds or animal matter. Nevertheless, males and females appeared to be opportunistic foragers, with similar feeding strategies throughout the year. A comparative analysis of stomach contents showed that the diets of males and nonpregnant females were quite comparable, while significant differences occurred in gravid females (especially of the two smallest species). Intra-individual differences gradually decreased from O. capito to T. tajacu, possibly as a result of closer male and female cohabitation as well as lower relative energy and protein requirements for pregnant females of the larger species. Finally, for the two smallest species, reproductive activity was correlated with seed and (or) animal matter intake.
Escape by a refuging prey, the broad-headed skink (Eumeces laticeps)
Authors: Cooper Jr. William E.
Published: April 2008

Factors influencing escape to refuge by the broad-headed skink (Eumeces laticeps) were examined by multiple regression and correlation of quantitative escape variables and distance and direction to refuge. I simulated a predator by walking toward a lizard and recorded aspects of escape. Approach distance (distance from me when escape began) increased with distance and angle to refuge, suggesting that the skinks assessed that risk increased with relative times required for prey and predator to reach the refuge. Distance fled was affected jointly by distance from the predator when escape began and distance to refuge; it increased with distance to refuge. It also increased with the angle between the predator's path and refuge due to declining distance from the predator per unit distance fled. Direction to the nearest refuge and direction fled were nearly identical. Distance and direction to refuge should strongly affect escape behaviour in prey that are active some distance from refuges but rely on them to avoid predation. These relationships may be weaker or absent in anachoric species (those nearly continuously occupying refuges) and those remaining close to refuges, as well as in species relying more on speed and fleeing for long distances than on refuges.
Phylogenetic analysis of the rumen ciliate family Ophryoscolecidae based on 18S ribosomal RNA sequences, with new sequences fromDiplodinium,Eudiplodinium, andOphryoscolex
Authors: Wright André-Denis G. , Lynn Denis H.
Published: April 2008

Phylogenetic relationships within the largest family of entodiniomorphid rumen ciliates, the Ophryoscolecidae, were inferred from comparisons of small-subunit ribosomal RNA gene sequences. These included three new sequences from Diplodinium dentatum (1638 base pairs (bp)), Eudiplodinium maggii (1637 bp), and Ophryoscolex purkynjei (1636 bp). Using morphological characters, Lubinsky constructed a cladogram of the Ophryoscolecidae, and on the basis of his analysis, he divided the family into three subfamilies (Entodiniinae, Diplodiniinae, Ophryoscolecinae) to reflect his "natural" groupings (G. Lubinsky. 1957. Can. J. Zool. 35: 141 – 159). Our cladistic analysis, based on the limited morphological and ultrastructural data available, indicates that there are no synapomorphies supporting the Diplodiniinae sensu Lubinsky. However, based upon the six 18S sequences for the Ophryoscolecidae, the rumen ciliates are monophyletic and fall into three distinct groups corresponding to Lubinsky's subfamilial division of the family. Our molecular analysis shows Entodinium to be the earliest branching rumen ciliate (subfamily Entodiniinae) and Eudiplodinium, not Diplodiium, branching first among the diplodiniines.
The effects of molt on the flight performance, body mass, and behavior of European starlings (Sturnus vulgaris): an experimental approach
Authors: Swaddle John P. , Witter Mark S.
Published: April 2008

The physiological and energy costs of avian molt are well documented, but indirect consequences such as changes in flight performance have received less attention. Here, we report two experiments that investigated flight performance, body mass regulation, and behavior in captive starlings (Sturnus vulgaris). In the first experiment, we found a U-shaped change in take-off escape performance during natural molt: birds ascended at the shallowest trajectories during midmolt. Birds' body mass was also reduced during molt. In the second experiment, we manipulated the plumage of starlings to simulate different stages of flight-feather molt. This allowed us to separate the aerodynamic costs of feather loss from the physiological costs of feather synthesis normally associated with plumage growth. Through observations of flight (take-off, aerial maneuverability, and level flapping-flight speed) and behavioral parameters, we demonstrated that birds in simulated molt have reduced flight performance and reduced body mass. These birds also decrease the time spent performing energetically costly activities and seek areas of relative protection. In the longer term, some aspects of performance return to pretreatment levels, implying compensation for the plumage manipulations. Our results demonstrate that molt incurs significant functional costs that may play an important role in the adaptive radiation of molt strategies and molt patterns observed in avian species.
Type II microtrich sensilla of amphipods: variations in external morphology and distributional patterns
Authors: Steele V. J. , Steele D. H.
Published: April 2008

Scanning electron microscopic observations of type II microtrichs on the integument of selected amphipods show that these sensilla vary in length from less than 2 to 25 μm and, with few exceptions, their external morphology is similar. Typically, these microtrichs occur in two dorsal and two lateral clusters on each somite. Exceptionally, there is a series of circumferential clusters. Sexually mature males of some amphipod species have many additional lateral clusters on somite 11. Type II microtrichs are also present on the telson but absent from the head. The most prevalent cluster pattern is a row in the form of a J, but this may be modified into a Y, a semicircle, or a curvilinear pattern.