bluuebunny/crossref_metadata_2025_split huggingface dataset:
Decay of momentum flux in submerged jets
Authors: Schneider Wilhelm 
Published: April 2006

Slender laminar and turbulent, plane and axisymmetric jets emerging from orifices in plane or conical walls are studied at large distances from the orifices. The entrainment of momentum coupled with the entrainment of volume into a jet is determined, and its effect on the flow field is analysed by combining inner and outer expansions with a multiple scaling approach.In turbulent (plane or axisymmetric) jets, the axial velocity decreases more rapidly than predicted by classical boundary-layer solutions, and the momentum flux vanishes as the distance from the orifice tends to infinity. The analysis unveils a source of discrepancies in previous experimental data on turbulent jets.In a laminar plane jet, the momentum flux changes but little. In a laminar axisymmetric jet, the momentum flux changes slowly, yet considerably. When a critical distance from the orifice is approached, the momentum flux in the jet becomes very small, the jet diameter very large, and a toroidal viscous eddy is predicted. The structure of the flow field is briefly discussed.
Modelling of porous media by renormalization of the Stokes equations
Authors: Kim Sangtae , Russel William B. 
Published: April 2006

The permeability of a random array of fixed spheres has been calculated over the range of volume fractions from dilute to almost closest packing, by assuming pairwise-additive (low-Reynolds-number) hydrodynamic interactions within an effective medium. Non-convergent pair interactions arising from the long-range decay of the Stokeslet were removed by renormalizing the Stokes equation to determine the permeability of the effective medium, i.e. to include the mean screening effect of the other spheres. Pair interactions in this Brinkman medium were calculated by the method of reflections in the far field and boundary collocation in the near field.The permeability predicted by the theory asymptotes correctly to established results for dilute arrays, and compares favourably (within 15%) with the Carman correlation for volume fractions between 0.3 and 0.5. The magnitude also falls within the range of exact results for periodic arrays at the higher concentrations, but our model does not reproduce the dependence on structure.Use of the Brinkman equation with an effective viscosity leads to an apparent slip velocity at the boundary of a porous medium. Our calculation of the bulk stress via volume averaging determines the effective viscosity and hence the slip coefficient unambiguously for dilute porous media. However, at concentrations corresponding to the available experimental results the lengthscale characterizing pressure or velocity gradients becomes comparable to the interparticle spacing, and the averaging technique fails. Indeed the Brinkman equation itself is no longer valid.
Boundary-layer development on the afterbody of an engine nacelle
Authors: Lai Eugene , Squire L. C. 
Published: April 2006

Measurements have been made of the pressure distribution and turbulent-boundary-layer development on the afterbody of a model engine nacelle with a jet exhausting from the base and with the jet replaced by a parallel solid sting. It was found that the effect of replacing the jet by a solid body was to increase the pressure recovery over the afterbody and hence give a lower drag than with the jet. These changes in the pressure distribution affected the boundary-layer development and turbulence structure by different methods based on a momentum integral equation and the kinetic equation for the turbulence. Both methods approximately incorporate the effects of convergence and divergence of the flow caused by changes in transverse curvature of the surface. Neither method was completely satisfactory for the prediction of the overall boundary-layer development.It was also found that, near the tail of the model, where the body radius is decreasing rapidly, the Reynolds shear stress was much lower than it would be in a two-dimensional boundary layer with the same pressure gradient. Calculations and analysis based on earlier work show that this reduction is directly related to the rates of strain associated with the convergence of the streamlines over the afterbody.
Speed of onset of bronchodilator response to salbutamol inhaled via different devices in asthmatics: a bioassay based on functional antagonism
Authors: Lavorini Federico , Geri Pietro , Mariani Laura , Marmai Cecilia , Maluccio Nazzarena Maria , Pistolesi Massimo , Fontana Giovanni A. 
Published: April 2006

AimsTo evaluate the speed of onset of bronchodilation following salbutamol administered via a metered‐dose inhaler with a spacer (pMDI + Volumatic) and a dry‐powder inhaler (Diskus), as well as the relative potencies of these devices in asthmatic patients with methacholine‐induced bronchoconstriction.MethodsEighteen patients inhaled methacholine (MCh) until FEV1 decreased by 35% of control. Following administration of placebo, 200 µg salbutamol or 400 µg salbutamol through the pMDI + Volumatic or the Diskus, we calculated the time elapsed from drug administration and the appearance of a 90% increase in post‐MCh forced vital capacity (FVC), FEV1 and volume‐adjusted mid‐expiratory flow (recovery times). The salbutamol doses to be delivered by the two inhalation devices to achieve similar recovery times and the relative potencies of the devices were calculated by using the 2‐by‐2 Finney parallel regression method.ResultsFor all functional variables, recovery times were significantly (P < 0.01) shorter in pMDI + Volumatic than Diskus trials. The salbutamol doses to be delivered by the Diskus to achieve recovery times for FVC, FEV1 and volume‐adjusted mid‐expiratory flow similar to those obtained with 200 µg salbutamol administered via the pMDI + Volumatic were 558 (95% CI 537, 579) µg, 395 (95% CI 388, 404) µg and 404 (95% CI 393, 415) µg, respectively, and corresponded to relative potencies of 2.79 (95% CI 2.68, 2.90), 1.98 (95% CI 1.94, 2.02), and 2.02 (95% CI 1.96, 2.07).ConclusionsAdministration of salbutamol via the pMDI + Volumatic provides faster reversal of induced bronchoconstriction than via the Diskus. The salbutamol dose targeting the lungs with the pMDI + Volumatic is approximately twice that with the Diskus.
Effect of obesity and morbid obesity on the growth hormone (GH) secretion elicited by the combined GHRH + GHRP‐6 test
Authors: Kelestimur Fahrettin , Popovic Vera , Leal Alfonso , Van Dam P. Sytze , Torres Elena , Perez Mendez Luisa F. , Greenman Yona , Koppeschaar Hans P. F. , Dieguez Carlos , Casanueva Felipe F. 
Published: April 2006

SummaryObjective  Obesity is characterized by low basal levels of growth hormone (GH) and impeded GH release. However, the main problem arises in the diagnosis of GH deficiency in adults, as all accepted cut‐offs in the diagnostic tests of GH reserve are no longer valid in obese subjects. In this work, the role of obesity in the GH response elicited by the GHRH + GHRP‐6 test was assessed in a large population of obese and nonobese subjects.Patients  GHRH + GHRP‐6‐induced GH peaks were evaluated in 542 subjects. One hundred and five were healthy obese, 50 were morbid obese, and 261 were nonobese (both normal weight and overweight). One hundred and seventy‐six GH‐deficient patients (obese and nonobese) were also studied.Results  A regression analysis of the 366 subjects with normal pituitary function indicated that adiposity had a negative effect on the elicited GH peak (r = –0·503, P < 0·0001). A receiver operating characteristic (ROC) curve analysis showed that in subjects with a BMI 35, the currently accepted cut‐offs of the GHRH + GHRP‐6 test (GH peaks 20 µg/l: normal secretion; GH peaks 10 µg/l: GH deficiency), were fully operative. However, in subjects with a BMI > 35, normality was indicated by GH peaks 15 µg/l and GH deficiency by peaks 5 µg/l (1 µg/l = 2·6 mU/l).Conclusions  This study confirms: (a) that the combined provocative test is adequate to separate normal and GH‐deficient subjects; (b) the negative effect of obesity on GH secretion; (c) that obesity accounts for 25% of the reduction of GH release; and (d) that present cut‐off values are applicable to normal weight, overweight and grade I obesity subjects, whereas in obese subjects with a BMI exceeding 35, all the normative limits of the GHRH‐GHRP +6 test must be reduced by 5 µg/l.
The relationship between four single nucleotide polymorphisms in the promoter region of the osteoprotegerin gene and aortic calcification or coronary artery disease in Koreans
Authors: Rhee Eun Jung , Oh Ki Won , Jung Chan Hee , Lee Won Young , Oh Eun Sook , Yun Eun Joo , Baek Ki Hyun , Kang Moo Il , Kim Sun Woo 
Published: April 2006

SummaryObjective  Osteoprotegerin (OPG) is a recently identified cytokine that acts as a decoy receptor for the receptor activator of the NF‐κB ligand (RANKL). OPG has been shown to be an important inhibitor of osteoclastogenesis and arterial calcification in animal models. OPG has been proposed as a link molecule between osteoporosis and arterial calcification, but the relationship between the OPG gene and the cardiovascular system in human populations is unclear. Thus, the aim of this study was to investigate the relationship between OPG gene polymorphisms and aortic calcification or coronary artery disease in Koreans.Design and patients  Genotyping of four polymorphisms, A163G, G209A, T245G and T950C, in the promoter region of the OPG gene was performed in 251 healthy Korean women (mean age 51·3 ± 6·9 years) and in a second study population consisting of 100 patients who underwent coronary angiography (mean age 57·0 ± 11·9 years), by allelic discrimination using the 5′ nuclease polymerase chain reaction assay. Cardiovascular risk factors and serum OPG levels were measured and aortic calcification in thoracic and abdominal aorta was examined by simple radiological methods.Results  In the first study population, the prevalence of aortic calcification increased significantly as the subjects grew older. The frequencies of mutant alleles were significantly higher in the subjects with aortic calcification compared with those without aortic calcification in G209A and T950C polymorphisms, although these significances were lost after adjustment for age. No significant relationship was found between OPG gene polymorphisms and serum OPG levels or cardiovascular risk factors. In the second study group, there were no associations between OPG promoter genotypes and aortic calcification, serum OPG levels, or coronary artery disease.Conclusions  We observed that the four polymorphisms in the promoter region of the OPG gene were not associated with aortic calcification or coronary artery disease in Koreans. Further studies are needed to clarify this relationship.
Estimation of the longevity of C in terrestrial detrital food webs using radiocarbon (14C): how old are diets in termites?
Authors: HYODO F. , TAYASU I. , WADA E. 
Published: April 2006

SummaryWe propose that diets of consumers in a food web have various ages, where age is defined as the time elapsed since carbon (C) in the diet was fixed from atmospheric CO2by primary producers. To examine the diet ages for primary consumers in a detrital food web, we measured the radiocarbon (14C) content of termites collected in Thailand in 1998 and 2004. Diet ages were estimated by comparing the14C content of samples with records of atmospheric14CO2, which doubled in the early 1960s as a result of nuclear weapons tests and decreased after the nuclear test ban treaty. For comparison, we measured the14C content of bees as primary consumers in a grazing web at the same study site. Stable carbon and nitrogen (N) isotope ratios were also analysed.The14C contents of the same species of termites decreased during the sampling interval, indicating that they used organic matter produced after the peak in atmospheric14CO2. The diet ages were estimated to be 12–18, 7–13 and 5–9 years for the wood‐feeder (Microcerotermes crassus), the soil‐feeders (Dicuspiditermes makhamensisandTermes comis) and the fungus‐grower (Macrotermes carbonarius), respectively. One colony of soil‐feeder (T. comis), which nested in a fallen tree trunk, had exceptionally low14C content, and its diet age was estimated to be around 50 years. The two bee species had lower14C contents compared with the termites, and their diet ages were estimated to be 0 (Apis florea) and 2–4 years (Trigonasp.).Stable C and N isotope ratios of termites showed similar patterns as previously reported, and no clear difference was observed between 1998 and 2004. Although the bees and the fungus‐growing termite had similar stable C and N isotope ratios, their diet ages differed.Our study suggests that radiocarbon can be used to estimate the diet ages of consumers in terrestrial food webs. Diet age should provide new insight into the trophic positions of organisms in grazing and detrital food webs and the interactions between these two webs.
Ontogenetically stable hydraulic design in woody plants
Authors: WEITZ J. S. , OGLE K. , HORN H. S. 
Published: April 2006

Summary

An important component of plant water transport is the design of the vascular network, including the size and shape of water‐conducting elements or xylem conduits.
For over 100 years, foresters and plant physiologists have recognized that these conduits are consistently smaller near branch tips compared with major branches and the main stem. Empirical data, however, have rarely been assembled to assess the whole‐plant hydraulic architecture of woody plants as they age and grow.
In this paper, we analyse vessels of Fraxinus americana (White Ash) within a single tree. Vessels are measured from cross‐sections that span 12 m in height and 18 years’ growth.
We show that vessel radii are determined by distance from the top of the tree, as well as by stem size, independently of tree height or age.
The qualitative form for the scaling of vessel radii agrees remarkably well with simple power laws, suggesting the existence of an ontogenetically stable hydraulic design that scales in the same manner as a tree grows in height and diameter.
We discuss the implications of the present findings for optimal theories of hydraulic design.
Effects of climate on oxygen consumption and energy intake of chromosomally divergent populations of the House Mouse (Mus musculus domesticus) from the island of Madeira (North Atlantic, Portugal)
Authors: MATHIAS M. L. , NUNES A. C. , MARQUES C. C. , AUFFRAY J.‐C. , BRITTON‐DAVIDIAN J. , GANEM G. , GÜNDÜZ I. , RAMALHINHO M. G. , SEARLE J. B. , SPEAKMAN J. R. 
Published: April 2006

Summary

We explored the effects of climatic variables (mean altitude, mean daily winter temperature, mean daily summer temperature, mean annual precipitation and days of precipitation per year) on energetic parameters (food intake and resting oxygen consumption) in six Robertsonian chromosomal races and hybrid populations of House Mice (Mus musculus domesticus) collected throughout the island of Madeira in the North Atlantic.
Food energy intake and resting metabolism (oxygen consumption) were measured, in 59 non‐reproducing adult males trapped in April–September 1998 and June 1999 and maintained in captivity for at least 3 weeks prior to measurements.
Mean daily energy intake of Robertsonian mice varied between 25·3 kJ day−1 in race S. Vicente (2n = 25–27) and 34·6 kJ day−1 in race Achadas da Cruz (2n = 24–27), while in hybrids (2n = 22 × 2n = 40) it was 23·0 kJ day−1. All races exhibited low resting rates of oxygen consumption compared with the predicted basal metabolic rates expected for Muridae, between 49·2% and 66·5% of the expected values.
The main factor influencing both food energy intake and oxygen consumption was body mass, explaining 41% of the variation in food energy intake and 39% of the variation in resting oxygen consumption. Body mass was significantly related to the mean summer temperature at the sites where the mice were captured, but was unaffected by the chromosomal race or other biogeographical and climatic variables. There were no additional effects of these factors on resting oxygen consumption beyond the effect of body mass.
Once the effects of body mass were removed, food energy intake was significantly correlated with the chromosomal race. The different environmental conditions experienced by the races may have favoured the physiological adaptation of mice to different habitats.
Chemical composition and digestibility of Trifolium exposed to elevated ozone and carbon dioxide in a free‐air (FACE) fumigation system
Authors: MUNTIFERING R. B. , CHAPPELKA A. H. , LIN J. C. , KARNOSKY D. F. , SOMERS G. L. 
Published: April 2006

Summary

Tropospheric ozone (O3) and carbon dioxide (CO2) are significant drivers of plant growth and chemical composition. We hypothesized that exposure to elevated concentrations of O3 and CO2, singly and in combination, would modify the chemical composition of Trifolium and thus alter its digestibility and nutritive quality for ruminant herbivores.
We tested our hypothesis by collecting samples of Red Clover (Trifolium pratense) and White Clover (Trifolium repens) from the understoreys of Trembling Aspen (Populus tremuloides)–Sugar Maple (Acer saccharum) communities that had been exposed since 1998 to ambient air, elevated CO2, elevated O3 or elevated CO2 + O3 at the Aspen Free‐Air CO2 and O3 Enrichment (FACE) site located near Rhinelander, WI, USA. Foliage samples were analysed for (1) concentrations of N, total cell wall constituents, lignin and soluble phenolics; and (2) in vitro dry‐matter digestibility (IVDMD) and in vitro cell‐wall digestibility (IVCWD) using batch cultures of ruminal micro‐organisms.
Significant air‐treatment effects were observed for lignin concentration, IVDMD and IVCWD, and between Red and White Clover for all dependent variables. No air treatment × clover species interactions were detected.
Exposure to elevated O3 resulted in increased concentration of lignin and decreased IVDMD and IVCWD compared with exposure to ambient air, and the response was similar regardless of whether plants had been coexposed to elevated CO2. Exposure to elevated CO2 alone did not affect chemical composition or in vitro digestibility, nor did it ameliorate the negative effect of elevated O3 on these determinants of nutritive quality for ruminant herbivores.
In contrast to recent reports of a protective effect of elevated CO2 against growth reduction in plants under O3 stress, our results indicate that elevated CO2 would not be expected to ameliorate the negative impact of elevated O3 on nutritive quality of Trifolium under projected future global climate scenarios.
Earthworms (Lumbricus terrestris) affect plant seedling recruitment and microhabitat heterogeneity
Authors: MILCU A. , SCHUMACHER J. , SCHEU S. 
Published: April 2006

SummaryThe effects of the anecic earthwormLumbricus terrestrisL. on plant seedling recruitment and spatial aggregation were investigated in a microcosm glasshouse experiment by varying plant seed size (small and large); functional groups (grasses, legumes, herbs); plant species diversity (1, 3, 6); and plant functional group diversity (1, 3).Generally, earthworms buried seeds quickly irrespective of seed size and species. Secondary seed dispersal (phase II dispersal) by earthworms affected plant community composition depending mainly on seed size but less on plant functional group identity and diversity: small‐seeded species were repressed whereas large‐seeded were promoted.Although, in general, recruitment of seedlings was less in the presence ofL. terrestris, recruited seedlings benefited from establishing in the vicinity of earthworm burrows. The strong aggregation of plants in the vicinity of earthworm burrows resulted in plant communities with a more heterogeneous small‐scale architecture. Earthworm burrows and middens acted as an important regeneration niche for emergent seedlings by reducing microsite and nutrient limitations.In conclusion, seed dispersal, seed burial, seedling recruitment, and the spatial distribution of seedlings of plant species of different functional groups and with a wide range of seed size are strongly affected byL. terrestris, and this probably affects plant community composition.
Stress‐mediated covariance between nano‐structural architecture and ultraviolet butterfly coloration
Authors: KEMP D. J. , VUKUSIC P. , RUTOWSKI R. L. 
Published: April 2006

Summary

Structural coloration is a striking component of sexual ornamentation, and may function as a signal of mate quality. Although the proximate optical mechanisms are often well defined, we know much less about the morphological basis for intraspecific variation in structural colour.
Males of the butterfly Colias eurytheme L. possess a thin‐film interference array on their dorsal wing scales that generates a bright and iridescent ultraviolet (UV) signal. This signal is used in mate choice.
Using scanning electron microscopy, we investigated the covariance between nano‐structural architecture and UV reflectance in samples that were variously subject to either nutrient stress (using a larval host‐plant manipulation), or thermal stress (using transient heat and cold shocks during the pupal period). We employed these two stressors to mimic natural stressful processes and to accentuate the variance in UV signal characteristics.
Two primary structure–reflectance relationships were apparent. First, UV brightness increased with the density of scale ridges that bear the interference reflectors. Second, the breadth of above‐wing angles for viewing the UV covaried with a measure of thin‐film angular orientation. These relationships were, however, either limited to, or stronger among, males of the nutrient stress sample.
Our results are consistent with a causal effect of developmental stress on nano‐structural architecture and henceforth UV reflectance, but also suggest that the proximate basis for signal variation may be intimately linked to the nature of prevailing stressors.
Short‐ and long‐term consequences of thermal variation in the larval environment of anurans
Authors: NIEHAUS AMANDA C. , WILSON ROBBIE S. , FRANKLIN CRAIG E. 
Published: April 2006

Summary

To survive adverse or unpredictable conditions in the ontogenetic environment, many organisms retain a level of phenotypic plasticity that allows them to meet the challenges of rapidly changing conditions. Larval anurans are widely known for their ability to modify behaviour, morphology and physiological processes during development, making them an ideal model system for studies of environmental effects on phenotypic traits. Although temperature is one of the most important factors influencing the growth, development and metamorphic condition of larval anurans, many studies have failed to include ecologically relevant thermal fluctuations among their treatments.
We compared the growth and age at metamorphosis of striped marsh frogs Limnodynastes peronii raised in a diurnally fluctuating thermal regime and a stable regime of the same mean temperature. We then assessed the long‐term effects of the larval environment on the morphology and performance of post‐metamorphic frogs.
Larval L. peronii from the fluctuating treatment were significantly longer throughout development and metamorphosed about 5 days earlier. Frogs from the fluctuating group metamorphosed at a smaller mass and in poorer condition compared with the stable group, and had proportionally shorter legs.
Frogs from the fluctuating group showed greater jumping performance at metamorphosis and less degradation in performance during a 10‐week dormancy. Treatment differences in performance could not be explained by whole‐animal morphological variation, suggesting improved contractile properties of the muscles in the fluctuating group.