bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical stretch‐induced hypertrophy of neonatal rat ventricular myocytes is mediated by β1‐integrin‐microtubule signaling pathways
Authors: Yutao Xi , Geru Wu , Xiaojun Bai , Tao Geng , Aiqun Ma
Published: September 2005

Background:

Mechanical stress plays a crucial role in tissue morphogenesis and remodeling. These processes depend in part on force transmission mediated through integrins and the cytoskeleton.

Methods:

Ventricular myocytes isolated from neonatal Sprague–Dawley rats (NRVMs) were exposed to persistent centrifugal force stretch for 12 or 24 h. The NRVMs were exposed to colchicine (4 μmol/ml) and anti‐integrin β1 specific antibody (10 μg/ml). Cell viability was assessed by MTT assay and lactate dehydrogenase (LDH) activity. Incorporation of 3H‐leucine, and atrial natriuretic peptide (ANP) and angiotensin II (Ang II) levels were assessed. Pixel intensity and distribution of the microtubule were estimated from laser scanning confocal images.

Results:

Changes in LDH release and the MTT assay showed that 180 rpm. centrifugal force had minimal effect on the viability and number of NRVMs. Mechanical stretch significantly increased 3H‐leucine incorporation into cardiomyocytes. Anti‐integrin β1 blocking antibody effectively inhibited the increase in 3H‐leucine incorporation and release of ANP (p<0.05). Following anti‐integrin‐β1‐blocking antibody, the pixel intensity of the microtubule image was decreased after both12 and 24 h stretch, this was similar to the effect of colchicine. Both treatments also inhibited the secretion of Ang II induced by stretch (p<0.05).

Conclusions:

Anti‐integrin‐β1‐blocking antibody and colchicine had similar effects, partly inhibiting the stretch‐induced increase in microtubule polymerization and the secretion of Ang II in hypertrophic cardiac myocytes.
Early changes in serum markers of cardiac extra‐cellular matrix turnover in patients with uncomplicated hypertension and type II diabetes
Authors: Alla François , Kearney‐Schwartz Anna , Radauceanu Anca , Dores Sylvie Das , Dousset Brigitte , Zannad Faiez
Published: September 2005

Aims:

Extracellular matrix (ECM) turnover is a major determinant of diastolic dysfunction and pumping capacity, thus potentially contributing to the progression of congestive heart failure (CHF). Patients with both arterial hypertension and diabetes have a high risk of heart failure. Whether these patients have changes in cardiac ECM has not been studied previously. Our objective was to compare blood markers of collagen turnover among patients with CHF, patients with hypertension and type II diabetes (HD), and healthy individuals.

Methods and results:

Measurements were performed in 239 CHF patients; 64 HD patients and 92 healthy subjects. We showed by adjusted ANOVA that PIIINP levels were significantly higher in CHF and HD patients than in controls, and higher in CHF patients than in HD patients. MMP1 levels were significantly lower in CHF and HD patients than in controls. Collagen type I markers (PICP and PINP) were not influenced by CHF but were lower in HD patients as compared to controls (p<0.05 for all comparisons).

Conclusion:

In heart failure, markers of cardiac collagen synthesis are increased and markers of degradation are decreased, potentially contributing to cardiac fibrosis and thus to poor outcome. Changes in collagen turnover may also occur early in the disease process in high‐risk patients before heart failure is clinically detectable.
Angiotensin II AT1 receptor density on blood platelets predicts early left ventricular remodelling in non‐reperfused acute myocardial infarction in humans
Authors: Maczewski Michal , Borys Marcin , Kacprzak Pawel , Gdowski Tomasz , Wojciechowski Dariusz
Published: September 2005

Background:

Renin—angiotensin‐system activity, a principal factor determining ventricular remodelling after myocardial infarction (MI), is dependant on local angiotensin II concentration and angiotensin AT1 receptor (AT1R) density. The latter is regulated by systemic factors acting independently from angiotensin II concentration.

Objective:

To test the hypothesis that AT1R density at the onset of MI determines post‐MI ventricular remodelling.

Methods:

In 48 patients with first acute MI who did not undergo reperfusion therapy, angiotensin AT1R density on blood platelets (reflecting cardiovascular AT1R density) was assessed 13±5 h after the onset of MI, using radioligand binding assay. Left ventricular end‐systolic (LVESVI) and end‐diastolic volume indices (LVEDVI) and ejection fraction (EF) were assessed by two‐dimensional echocardiography as measures of ventricular remodelling.

Results:

Predischarge LVESVI and LVEDVI positively and EF negatively correlated with AT1R density. Patients with AT1R density below median had significantly lower LVESVI (33.2±2.4 mL/m2), LVEDVI (70.0±2.8 mL/m2) and higher EF (52.8±2.3%) than patients with AT1R density above median (LVESVI=44.9±2.6, LVEDVI=81.3±3.9 mL/m2 and EF=44.9±2.6%, all p<0.01). In multivariate analysis, only AT1R density and infarct size were independent predictors of early post‐MI ventricular dilation.

Conclusions:

High density of AT1R at the onset of MI is a predictor of early left ventricular remodelling.
Expression of macrophage‐selective markers in human and rodent adipocytes
Authors: Khazen Wael , M'Bika Jean-Pierre , Tomkiewicz Céline , Benelli Chantal , Chany Charles , Achour Ammar , Forest Claude
Published: September 2005

CD14, CD68 and/or mouse F4/80 or human epidermal growth factor module‐containing mucin‐like receptor 1 (EMR1) are widely used as macrophage‐specific markers. Since macrophages infiltrate several tissues during inflammatory processes, CD14, CD68 and EMR1‐F4/80 have been employed to discriminate between tissue‐containing macrophages, like adipose tissue (AT), and other cells. Using real‐time PCR experiments, we show that isolated adipocytes from humans and mice AT express high levels of CD14 and CD68 mRNA, whereas EMR1‐F4/80 is mainly present in the macrophage‐containing stroma‐vascular fraction. Furthermore, fibroblasts‐like cells (adipoblasts), preadipocytes and adipocytes from the murine cell lines, 3T3‐F442A and BFC‐1, express CD14 and CD68 mRNA and protein as determined by fluorescence‐activated cell sorter, but not F4/80 which, as expected, is strongly expressed in the macrophage cell line RAW264.7. These results reinforce the view that EMR1‐F4/80 is the best macrophage marker to date and show that CD14 and CD68 are not macrophage‐specific proteins.
Determinants of the nucleolar targeting of protein phosphatase‐1
Authors: Lesage Bart , Beullens Monique , Ceulemans Hugo , Himpens Bernard , Bollen Mathieu
Published: September 2005

The ubiquitously expressed protein Ser/Thr phosphatase‐1 isoforms PP1α, PP1β and PP1γ1 are dynamically targeted to distinct, but overlapping cellular compartments by associated proteins. Within the nucleus of HeLa cells, EGFP‐tagged PP1γ1 and PP1β were predominantly targeted to the nucleoli, while PP1α showed a more diffuse distribution. Using PP1 chimaeras and point mutants we show here that a single N‐terminal residue, i.e., Gln20 for PP1α, Arg19 for PP1β and Arg20 for PP1γ1 accounts for their distinct subnuclear distribution. Our data also suggest that the N‐terminus of PP1β and PP1γ1 harbours an interaction site for one or more nucleolar interactors.
Activation of phospholipase D by 8‐Br‐cAMP occurs through novel pathway involving Src, Ras, and ERK in human endometrial stromal cells
Authors: Yoon Mee-Sup , Koo Jun Bon , Hwang Jung-Hye , Lee Ki Sung , Han Joong-Soo
Published: September 2005

We investigated the mechanism of 8‐Br‐cAMP‐mediated phospholipase D (PLD) activation using a primary cell culture system of human endometrial stromal cells (ES cells). PLD activity was increased by the treatment of ES cells with 8‐Br‐cAMP, maximally at 5 min. To determine whether the effects of 8‐Br‐cAMP on PLD occurred as a consequence of PKC activation, ES cells were preincubated for 15 min with RO320432 (1 μM) and GF109203X (1 μM), the PKC inhibitors, or they were pretreated for 24 h with phorbol myristate acetate (100 nM) to downregulate PKC. However, these treatments had no effects on PLD activation induced by 8‐Br‐cAMP. Furthermore, 8‐Br‐cAMP had no effects on the subcellular distribution of PKC α and PKC βI, confirming no involvement of PKC. 8‐Br‐cAMP activated ERK1/2, maximally at 5 min, and PD98059 (MEK inhibitor: 50 μM) and transfection of ES cells with dominant negative (DN)‐MEK completely inhibited 8‐Br‐cAMP‐induced PLD activation, suggesting that ERK1/2 mediates the PLD activation. To investigate the involvement of protein kinase A (PKA), Src, and Ras in 8‐Br‐cAMP‐induced PLD activation, we used PKA inhibitor, H89 and Rp‐cAMPs, and transfections of DN‐Src and DN‐Ras. H‐89 and Rp‐cAMPs completely blocked 8‐Br‐cAMP‐mediated PLD and ERK activation, implying the involvement of PKA in this PLD activation. In addition, transfection of ES cells with DN‐Src, or DN‐Ras partially inhibited 8‐Br‐cAMP‐induced ERK1/2 and consequently PLD activation, whereas cotransfection of DN‐Src and DN‐Ras completely inhibited ERK1/2 and PLD activation, suggesting that Src and Ras independently regulate ERK/PLD activation. Taken together, these results demonstrate a novel pathway in ES cells that 8‐Br‐cAMP activate PLD through PKA and ERK1/2 and this ERK/PLD activation by 8‐Br‐cAMP is mediated by Src and Ras, separately.
EFFECTS OF MANURE AND FERTILIZER ON GRAIN YIELD, SOIL CARBON AND PHOSPHORUS IN A 13-YEAR FIELD TRIAL IN SEMI-ARID KENYA
Authors: KIHANDA F. M. , WARREN G. P. , MICHENI A. N.
Published: September 2005

Long-term indicators of soil fertility were assessed by measuring grain yield, soil organic carbon (SOC) and soil Olsen phosphorous for a P-deficient soil. In one set of treatments, goat manure was applied annually for 13 years at 0, 5 and 10 t ha−1, and intercrops of sorghum/cowpea, millet/green gram and maize/pigeonpea were grown. Yield depended on rainfall and trends with time were not identifiable. Manure caused an upward trend in SOC, but 10 t ha−1 manure did not give significantly more SOC than 5 t ha−1. Only 10 t ha−1 manure increased Olsen P. Measurements of both SOC and Olsen P are recommended. In another set of treatments, manure was applied for four years; the residual effect lasted another seven to eight years when assessed by yield, SOC and Olsen P. Treatment with mineral fertilizers provided the same rates of N and P as 5 t ha−1 manure and yields from manure and fertilizer were similar. Fertilizer increased Olsen P but not SOC. Management systems with occasional manure application and intermediate fertilizer applications should be assessed. Inputs and offtakes of C, N and P were measured for three years. Approximately 16, 25 and 11% of C, N and P respectively were stabilized into soil organic matter from 5 t ha−1 a−1 manure. The majority of organic P was fixed as soil inorganic P.
GENETIC IMPROVEMENT AND COCOA YIELDS IN GHANA
Authors: EDWIN J. , MASTERS W. A.
Published: September 2005

This paper documents the yield gains attributable to the breeding and distribution of new cocoa varieties in Ghana, using data from a 2002 survey of 192 fields in the country's key cocoa producing regions. We find that planting the more recently-released varieties is associated with at least 42% higher yields, and that genetic improvement accounts for much but not all of the observed correlation between tree age and cocoa yield. Fertilizer use is also very important, being associated with 19% higher cocoa yield per 50 kg bag of fertilizer. We find no evidence that varieties differ in their response to fertilizer, pesticide use or labour, and no evidence of a decline in the yield advantage of new varieties over the 17-year age span observed in the sample.
Sensing the physical and nutritional status of the root environment in the field: a review of progress and opportunities
Authors: CLARK L. J. , GOWING D. J. G. , LARK R. M. , LEEDS-HARRISON P. B. , MILLER A. J. , WELLS D. M. , WHALLEY W. R. , WHITMORE A. P.
Published: September 2005

The challenge that faces agriculture at the start of the 21st Century is to provide security of food production in a sustainable way. Achieving this task is difficult enough, but against a background of climate change, it becomes a moving target. However, one certainty is that soil factors that limit crop growth must be taken into account as new strategies for crop management are developed. To achieve this, it is necessary to measure the physical and nutritional status of the root environment in the field. Before considering measurement methods, our understanding of how the plant interacts with its soil environment is reviewed, so that it is clear what needs to be measured. Soil strength due to soil drying is identified as an important stress that limits agricultural productivity. The scope to measure soil factors that directly affect plant growth is reviewed. While in situ sensors are better developed, progress in the development of remote sensors of soil properties are also reviewed. A robust approach is needed to interpret soil measurements at the field scale and here geostatistics has much to offer. The present review takes a forward look and explores how our understanding of plant responses to soil conditions, the newly emerging sensing technologies and geostatistical tools can be drawn together to develop robust tools for soil and crop management. This is not intended to be an exhaustive review. Instead, the authors focus on those aspects that they consider to be most important and where the greatest progress is being made.
Agronomic evaluation and performance of flax varieties for industrial fibre production
Authors: DIMMOCK J. P. R. E. , BENNETT S. J. , WRIGHT D. , EDWARDS-JONES G. , HARRIS I. M.
Published: September 2005

Flax fibre for industrial purposes differs from that for linen production, although the agronomic factors that influence fibre development and which factors are most important for industrial fibre production have still to be defined. A description of variations in the performance of fibre flax varieties is also necessary as current guidance relates to the European market rather than the UK. Field trials were sown in 2002 and 2003 at the Henfaes Research Centre in north Wales, investigating 29 and 26 varieties, respectively, of European fibre flax and dual-purpose flax varieties. In 2002 a nitrogen treatment was included in the trial with two treatments, 40 kg/ha and 80 kg/ha. Varieties were evaluated for 20 agronomic and fibre production variables, and the differences between the varieties were analysed using analysis of variance (ANOVA) and principal components analysis (PCA). The higher nitrogen rate was found to increase crop lodging, although some varieties were found to be more susceptible than others. Environment had a strong influence on crop success, with some varieties showing more year to year stability than others. PCA allowed those varieties that were the highest yielding, highest fibre producers and showed the best stability across the 2 years to be identified. Understanding the agronomic results presented and discussed here is important if fibre flax production is to become economically viable in the UK.
Proceedings of the Thirty-seventh Meeting of the Agricultural Research Modellers' Group
Authors: CROMPTON L. A. , WHEELER T. R.
Published: September 2005

This group, which is concerned with the applications of mathematics to agricultural science, was formed in 1970 and has since met at approximately yearly intervals in London for one-day meetings. The thirty-seventh meeting of the group, chaired by J. Craigon of The University of Nottingham, was held in the Kohn Centre at the Royal Society, 6 Carlton House Terrace, London on Friday, 8 April 2005 when the following papers were read.
Effects of genotype and environment on seed yield and quality of rice
Authors: KRISHNAN P. , SURYA RAO A. V.
Published: September 2005

Seed yield and seed quality determine much of the value of rice (Oryza sativa L.) crops to the producers. The effects of genotype and environment on seed yield and quality were investigated using 12 rice genotypes grown during 3 years (2000–2003) at four different sowing dates in India, where detailed environmental data were collected. Yield, seed weight, proportion of seed setting and quality in terms of potential seed longevity, proportion of discoloured seeds, seed leachate conductivity and percentage germination were evaluated. The results were subjected to analysis of variance and the influence of environmental factors was evaluated by correlation analysis. Analysis of variance suggested that proportion of seed setting, seed leachate conductivity, potential seed longevity, percentage seed germination and proportion of seed discoloration were influenced more by environmental effects than by genotypic effects. In contrast, yield, panicle number, seed weight, and proportion of high-density grains were influenced more by genotypic than by environmental effects. The significant interaction effects of genotype and environment for all characteristics were attributed to differential resistance of genotypes to lodging (caused by increased plant height, low radiation and excessive rain at the time of grain filling) and were associated with fewer panicles harvested, lower seed setting and lower seed weight. Correlation analysis suggested that warm weather conditions with high solar radiation and without excessive rains during grain filling stage gave the best rice seed yield with high quality.
Genetic diversity in four cabbage populations based on random amplified polymorphic DNA markers
Authors: KOUTITA O. , TERTIVANIDIS K. , KOUTSOS T. V. , KOUTSIKA-SOTIRIOU M. , SKARACIS G. N.
Published: September 2005

Genetic diversity in four local Greek cabbage open-pollinated populations was investigated using RAPD (Random Amplified Polymorphic DNA) DNA markers in 18 individual plants from each population. A total of 24 random primers detected 90 polymorphic bands in the four populations studied, with an average of 3·75 bands/primer. The mean between-population differentiation was close to 40%, leaving 60% for within-population diversity. The individual plants were grouped, based on the Jaccard coefficient, by clustering (Unweighted Pair Group Method and Arithmetic Average – UPGMA) and an ordination (Principal Coordinates Analysis – PCO) methods, resulting in 7 and 6 groups, respectively. In general, there was a notable similarity in the grouping of the individuals with these two methods. In addition, Nei's standard genetic distance between populations, as calculated on the basis of within-population gene frequencies, was employed to group the populations by the UPGMA method. Clustering results were in good agreement with previously reported results based on morphological descriptors applied to the same populations. It was concluded that RAPD markers could be exploited as alternative or supplementary tools to already established methods for the evaluation and classification of cabbage genetic resources.
Effect of nitrogen fertilization on the expression of slow-blasting resistance in rice
Authors: MUKHERJEE A. K. , MOHAPATRA N. K. , SURIYA RAO A. V. , NAYAK P.
Published: September 2005

The development of rice blast disease in four slow-blasting (SB) genotypes was compared with that in the fast-blasting (FB) genotype Karuna, under natural field epidemics over a period of 3 years at five levels of nitrogen, in order to determine if the application of high doses of nitrogen influenced the expression of disease progress in the SB types. The treatment effects were compared through estimation of nine parameters viz. (i) lesion number (LN); (ii) area under disease progress curve (AUDPC); (iii) relative area under disease progress curve (RAUDPC); (iv) logistic apparent infection rate (r); (v) Gompertz apparent infection rate (k); (vi) logit line intercept (logit-a); (vii) gompit line intercept (gompit-a); (viii) time required for the disease to reach 0·25 severity in logistic (T25r); and (ix) Gompertz (T25k) models. There was a significant increase in LN, AUDPC, RAUDPC, r and k with increased levels of nitrogen application in all genotypes, but the rate of increase in disease severity was much lower in SB genotypes than the FB one and did not lead to breakdown of resistance in the SB genotypes, since severity level was much below the economic injury level. Among the nine derived parameters for evaluation of resistance LN, AUDPC, RAUDPC, r and k were best. The AUDPC and RAUDPC had lower degrees of error variance compared with the other parameters and hence were considered superior measures for characterization of disease progress curves.
Resource competition in contour hedgerow intercropping systems involving different shrub species with mature and young tea on sloping highlands in Sri Lanka
Authors: DE COSTA W. A. J. M. , SURENTHRAN P.
Published: September 2005

Tea (Camellia sinensis) in Sri Lanka is grown predominantly on sloping highlands. Incorporating trees as hedgerows along contours is aimed at reducing erosion and improving soil fertility through addition of prunings as mulch. However, there could be significant competition for essential growth resources between the hedgerows and tea. The primary objective of this study was to determine the influence of six hedgerow species (Calliandra calothyrsus, Senna [Cassia] spectabilis, Eupatorium inulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) on mature (6-year-old) and young (6-month-old) tea. This study had three on-farm, long-term (from Nov 1998 to Dec 2002) field experiments. Experiment 1 had 12 treatment combinations with the six shrub species and two mulching treatments (i.e. hedgerow prunings added to the tea plot as a mulch, and unmulched) on mature tea plus a sole tea crop as control. The same was repeated on young tea in Experiment 2 to determine whether resource competition on young tea was greater than that on mature tea. Experiment 3 examined the effects of removing tree root competition on tea by cutting a 1-m deep trench between hedgerows and tea.

In all experiments, total tea yields of hedgerow intercrops, cumulated over the 50-month experimental period, were significantly lower (by 3–50%) than sole tea crops, thus indicating significant resource competition except in the case of mulched hedgerow systems involving Eupatorium and mature tea (18% yield increase). Removal of below-ground competition significantly increased tea yields by 11–19%. Addition of hedgerow prunings as a mulch significantly increased yields of both mature and young tea by 13–21%. Tea yields of hedgerow systems with Calliandra, Flemingia and Eupatorium showed greater yield reductions in young tea than in mature tea, but the opposite was shown with other hedgerow species. There was a significant negative linear relationship between tea yield and pruned biomass of hedgerows. Tea yields of all experiments showed significant negative correlations with several hedgerow characters, which are indicators of their competitive ability. These included hedgerow root density, canopy lateral spread, height and cross-section. In a majority of hedgerow systems, the available phosphorus content of topsoil (0–20 cm depth) was up to 51% lower compared to sole crops. It is concluded that incorporation of contour hedgerows in to an existing tea crop could result in significant resource competition with tea and thereby cause tea yield to decrease. However, there is scope for selection of hedgerow species that minimize competition through spatial and temporal complementarity with tea in resource capture.
Soil reaction, yields and herbage element content as affected by lime applied on established leys in a multi-site field trial
Authors: FYSTRO G. , BAKKEN A. K.
Published: September 2005

Surface liming as a means for controlling the soil reaction in established leys was investigated in a series of 4-year field trials. Application of 625, 1250, 2500 or 5000 kg CaO equivalents/ha in spring of the first year caused an immediate rise in pH in the top 0–25 mm of the soil. The rate and range of the response below 25 mm was related to the precipitation at the experimental sites. Lime-induced changes in pH were not dependent on the initial level of soil reaction, whereas the positive response in grass production was greater and more immediate at sites where pH was below 5·3 rather than above. The increases in yields of macro elements were, in most instances, relatively lower than the increases in dry matter (DM) yields. Important exceptions here were the yields of Ca in all cuts and P in the second cuts, and the yields of Mg when dolomite rather than limestone was applied. The concentration of Ca in the herbage was positively affected by liming according to ruminant needs. The same holds for the concentration of Mg when granulated or coarse dolomite was applied. Liming lowered herbage uptake of Mn, Co and Zn, whereas Mo uptake was increased. There appeared to be no consistent relationship between liming and the plant uptake of Fe and Cu. Dependent on the initial conditions, liming might both improve and worsen the trace element status of harvested herbage with respect to the demands of ruminant animals. It is concluded that frequent surface liming at low rates might be an appropriate strategy for adjusting the soil pH in semi-permanent and permanent pastures.
Translation initiation: structures, mechanisms and evolution
Authors: Marintchev Assen , Wagner Gerhard
Published: September 2005

Translation, the process of mRNA-encoded protein synthesis, requires a complex apparatus, composed of the ribosome, tRNAs and additional protein factors, including aminoacyl tRNA synthetases. The ribosome provides the platform for proper assembly of mRNA, tRNAs and protein factors and carries the peptidyl-transferase activity. It consists of small and large subunits. The ribosomes are ribonucleoprotein particles with a ribosomal RNA core, to which multiple ribosomal proteins are bound. The sequence and structure of ribosomal RNAs, tRNAs, some of the ribosomal proteins and some of the additional protein factors are conserved in all kingdoms, underlying the common origin of the translation apparatus. Translation can be subdivided into several steps: initiation, elongation, termination and recycling. Of these, initiation is the most complex and the most divergent among the different kingdoms of life. A great amount of new structural, biochemical and genetic information on translation initiation has been accumulated in recent years, which led to the realization that initiation also shows a great degree of conservation throughout evolution. In this review, we summarize the available structural and functional data on translation initiation in the context of evolution, drawing parallels between eubacteria, archaea, and eukaryotes. We will start with an overview of the ribosome structure and of translation in general, placing emphasis on factors and processes with relevance to initiation. The major steps in initiation and the factors involved will be described, followed by discussion of the structure and function of the individual initiation factors throughout evolution. We will conclude with a summary of the available information on the kinetic and thermodynamic aspects of translation initiation.
Prevalence of Escherichia coli O157 in lambs at slaughter in Rome, central Italy
Authors: BATTISTI A. , LOVARI S. , FRANCO A. , Di EGIDIO A. , TOZZOLI R. , CAPRIOLI A. , MORABITO S.
Published: September 2005

A study on the prevalence of the faecal carriage of Escherichia coli O157 in lambs was performed in the major slaughterhouse in Rome, central Italy, during 2002. A total of 643 animals, consisting of 378 weaned and 265 suckling lambs, were assayed for the presence of E. coli O157. Five O157-agglutinating E. coli strains were isolated (0·8%, 95% CI 0·3–1·9). Only one was positive to PCR specific for the eae gene and produced verocytotoxin VT2, with a VTEC O157 overall prevalence of 0·2% (95% CI 0·0–1·0), whereas one strain possessed the eae gene only. All the other isolates were negative for the presence of all the virulence genes considered. The animals were either from local farms or imported from Eastern Europe. The results suggest an age-specific difference since the microorganism was isolated only from 0·3% (95% CI 0·0–1·7) of weaned lambs, while all samples from suckling lambs tested negative. From this study, the overall risk of human exposure to pathogenic E. coli O157 from lamb meat consumption derived from the major slaughterhouse in Rome can be considered reasonably low, particularly when suckling lamb meat is considered.
Solar activity, cosmic rays, and Earth's temperature: A millennium‐scale comparison
Authors: Usoskin I. G. , Schüssler M. , Solanki S. K. , Mursula K.
Published: September 2005

Previous studies of a solar influence on climate variations have often suffered from the relatively short length of continuous direct solar observations of less than 400 years. We use two recently reconstructed series of the sunspot number and the cosmic ray flux to study this question over time intervals of up to nearly 1800 years. Comparison of the Sun‐related data sets with various reconstructions of terrestrial Northern Hemisphere mean surface temperatures reveals consistently positive correlation coefficients for the sunspot numbers and consistently negative correlation coefficients for the cosmic rays. The significance levels reach up to 99% but vary strongly for the different data sets. The major part of the correlation is due to the similarity of the long‐term trends in the data sets. The trend of the cosmic ray flux correlates somewhat better with the terrestrial temperature than the sunspot numbers derived from the same cosmogenic isotope data.
Timeseries of Polar Water properties in Fram Strait
Authors: Holfort Jürgen , Hansen Edmond
Published: September 2005

Timeseries of temperature and salinity of Polar Water in the East Greenland Current (EGC) and on the East Greenland shelf at 79°N are presented. The observations in the EGC are made in the 45–74 dbar layer carrying liquid freshwater from the Arctic Ocean to subarctic seas. The properties on the outer fringe of the EGC are dominated by shifts of the position of the East Greenland Front (EGF). In the inner part of the EGC and on the shelf the seasonal cycle of the properties are dominated by the annual cycle of sea ice freezing and melting. Comparing the observations with the World Ocean Atlas (WOA) and other climatologies demonstrates that the climatologies in the EGC and on the shelf at 79°N are poor due to poor data coverage.
High methane flux from an arctic floodplain (Indigirka lowlands, eastern Siberia)
Authors: van Huissteden J. , Maximov T. C. , Dolman A. J.
Published: September 2005

Methane fluxes from arctic tundra soils on a river terrace and floodplain in northeastern Siberia, measured with flux chambers, show a high spatial variability. The methane fluxes on the river terrace compare well with fluxes reported in other studies on tundra methane fluxes. The average methane flux is 4.3 mg CH4 m−2 hr−1, and the average flux for wet sites is 7.2 mg m−2 hr−1 and for dry sites 0.18 mg m−2 hr−1, with negative fluxes occurring locally. The fluxes from floodplain sites are considerably higher, with an average flux of 12.5 mg m−2 hr−1, an average for wet sites of 23.4 mg m−2 hr−1, and an average for dry sites of 1.6 mg m−2 hr−1. Multilinear regression demonstrates that the methane flux depends on both water table and active layer thickness. However, these factors alone cannot explain the large floodplain methane fluxes. We hypothesize that the large fluxes from floodplain sites are caused by (1) higher primary productivity of the floodplain vegetation and a high plant‐mediated transport of methane, and (2) enhanced supply of substrate for methanogens by sedimentation of particulate organic matter from flood water. Our results indicate that changes in discharge and organic matter transport of arctic rivers may have a considerable effect on arctic methane fluxes.
Prediction of sediment‐bound nutrient delivery from semi‐arid California watersheds
Authors: Gabet Emmanuel J. , Fierer Noah , Chadwick Oliver A.
Published: September 2005

Soil carbon (C), nitrogen (N), and phosphorus (P) are lost from hillslopes in particulate forms through soil erosion. The fate of the eroded C (e.g., sequestration or oxidation) may affect the global C budget, and delivery of N and P to waterbodies can lead to eutrophication. Whereas the magnitude of particulate nutrient losses may be similar to or greater than dissolved losses, it is rarely estimated. We couple a sediment delivery model with measurements of C, N, and P in soil to account explicitly for hillslope sediment transport processes that yield sediment‐bound nutrients to fluvial networks. The model is applied to a site in California dominated by coastal sage scrub and gopher‐rich grasslands. Although the magnitude of sediment delivery predicted by the model has been tested with reservoir sedimentation records, no data exist to test the predicted rates of nutrient delivery. Nevertheless, the model results are provocative; it predicts that losses of particulate C from sage covered hillslopes (23 kg/ha/yr) are nearly double that from grassland hillslopes (13 kg/ha/yr), despite a lower annual sediment yield from the sage hillslopes. The model predicts similar average annual N and P losses for sage and grasslands but dramatic differences in the frequency and magnitude of delivery events. Nutrient delivery from grasslands is chronic whereas delivery from the coastal sage is highly episodic, with large pulses driven by fire frequency. These results suggest that changes in the vegetation community can alter the delivery regime of sediment‐bound C, N, and P.
In search of the late Miocene–early Pliocene “biogenic bloom” in the Atlantic Ocean (Ocean Drilling Program Sites 982, 925, and 1088)
Authors: Diester‐Haass Liselotte , Billups Katharina , Emeis Kay C.
Published: September 2005

We reconstruct paleoproductivity at three sites in the Atlantic Ocean (Ocean Drilling Program Sites 982, 925, and 1088) to investigate the presence and extent of the late Miocene to early Pliocene “biogenic bloom” from 9 to 3 Ma. Our approach involves construction of multiple records including benthic foraminiferal and CaCO3 accumulation rates, Uvigerina counts, dissolution proxies, and geochemical tracers for biogenic and detrital fluxes. This time interval also contains the so‐called late Miocene carbon isotope shift, a well‐known decrease in benthic foraminiferal δ13C values. We find that the timing of paleoproductivity maxima differs among the three sites. At Site 982 (North Atlantic), benthic foraminifera and CaCO3 accumulation were both at a maximum at ∼5 Ma, with smaller peaks at ∼6 Ma. The paleoproductivity maximum was centered earlier (∼6.6–6.0 Ma) in the tropical Atlantic (Site 925). In the South Atlantic (Site 1088), paleoproductivity increased even earlier, between 8.2 Ma and 6.2 Ma, and remained relatively high until ∼5.4 Ma. We note that there is some overlap between the interval of maximum productivity between Sites 925 and 1088, as well as the minor productivity increase at Site 982. We conclude that the paleoproductivity results support hypotheses aiming to place the biogenic bloom into a global context of enhanced productivity. In addition, we find that at all three sites the δ13C shift is accompanied by carbonate dissolution. This observation is consistent with published studies that have sought a relationship between the late Miocene carbon isotope shift and carbonate preservation.
Oscillatory shear-driven gas flows in the transition and free-molecular-flow regimes
Authors: Hadjiconstantinou Nicolas G.
Published: September 2005

We investigate oscillatory shear-driven gas flows in the transition and free-molecular-flow regimes. Analytical results valid through slip flow and the early transition regime are obtained using a recently proposed, rigorous second-order slip model with no adjustable coefficients. Analytical solution of the collisionless Boltzmann equation provides a description of the high Knudsen number limit (Kn⪢1) including the bounded shear layers present in the limit of high oscillation frequency. These layers are analogous to the Stokes layers observed in the Kn⪡1 limit, but contrary to the latter, they exhibit a nonconstant wave speed as demonstrated by Park, Bahukudumbi, and Beskok in Phys. Fluids. 16, 317 (2004). All theoretical results are validated by direct Monte Carlo simulations. We find that the second-order slip results are in good agreement with direct simulation Monte Carlo (DSMC) solutions up to Kn≈0.4; in some cases these results continue to provide useful approximations to quantities of engineering interest, such as the shear stress, well beyond Kn≈0.5. The collisionless theory provides, in general, a good description of DSMC results for Kn≳10, while in the high frequency limit the agreement is very good for Knundsen numbers as low as Kn≈5.
Characterization of surface roughness effects on pressure drop in single-phase flow in minichannels
Authors: Kandlikar Satish G. , Schmitt Derek , Carrano Andres L. , Taylor James B.
Published: September 2005

Roughness features on the walls of a channel wall affect the pressure drop of a fluid flowing through that channel. This roughness effect can be described by (i) flow area constriction and (ii) increase in the wall shear stress. Replotting the Moody’s friction factor chart with the constricted flow diameter results in a simplified plot and yields a single asymptotic value of friction factor for relative roughness values of ε∕D>0.03 in the fully developed turbulent region. After reviewing the literature, three new roughness parameters are proposed (maximum profile peak height Rp, mean spacing of profile irregularities RSm, and floor distance to mean line Fp). Three additional parameters are presented to consider the localized hydraulic diameter variation (maximum, minimum, and average) in future work. The roughness ε is then defined as Rp+Fp. This definition yields the same value of roughness as obtained from the sand-grain roughness [H. Darcy, Recherches Experimentales Relatives au Mouvement de L’Eau dans les Tuyaux (Mallet-Bachelier, Paris, France, 1857); J. T. Fanning, A Practical Treatise on Hydraulic and Water Supply Engineering (Van Nostrand, New York, 1877, revised ed. 1886); J. Nikuradse, “Laws of flow in rough pipes” [“Stromungsgesetze in Rauen Rohren,” VDI-Forschungsheft 361 (1933)]; Beilage zu “Forschung auf dem Gebiete des Ingenieurwesens,” Ausgabe B Band 4, English translation NACA Tech. Mem. 1292 (1937)]. Specific experiments are conducted using parallel sawtooth ridge elements, placed normal to the flow direction, in aligned and offset configurations in a 10.03mm wide rectangular channel with variable gap (resulting hydraulic diameters of 325μm–1819μm with Reynolds numbers ranging from 200 to 7200 for air and 200 to 5700 for water). The use of constricted flow diameter extends the applicability of the laminar friction factor equations to relative roughness values (sawtooth height) up to 14%. In the turbulent region, the aligned and offset roughness arrangements yield different results indicating a need to further characterize the surface features. The laminar to turbulent transition is also seen to occur at lower Reynolds numbers with an increase in the relative roughness.
Flow of gaseous mixtures through rectangular microchannels driven by pressure, temperature, and concentration gradients
Authors: Naris S. , Valougeorgis D. , Kalempa D. , Sharipov F.
Published: September 2005

The flow of binary gaseous mixtures through rectangular microchannels due to small pressure, temperature, and molar concentration gradients over the whole range of the Knudsen number is studied. The solution is based on a mesoscale approach, formally described by two coupled kinetic equations, subject to diffuse scattering boundary conditions. The model proposed by McCormack substitutes the complicated collision term and the resulting kinetic equations are solved by an accelerated version of the discrete velocity method. Typical results are presented for the flow rates and the heat fluxes of two different binary mixtures (Ne–Ar and He–Xe) with various molar concentrations, in two-dimensional microchannels of different aspect (height to width) ratios. The formulation is very efficient and can be used instead of the classical method of solving the Navier–Stokes equations with slip boundary conditions, which is restricted by the hydrodynamic regime. Moreover, the present formulation is a good alternative to the direct simulation Monte Carlo method, which often becomes computationally inefficient.
Liquids: The holy grail of microfluidic modeling
Authors: Gad-el-Hak Mohamed
Published: September 2005

Traditional fluid mechanics edifies the indifference between liquid and gas flows as long as certain similarity parameters—most prominently the Reynolds number—are matched. This may or may not be the case for flows in nanodevices or microdevices. The customary continuum, Navier–Stokes modeling is ordinarily applicable for both air and water flowing in macrodevices. Even for common fluids such as air or water, such modeling is bound to fail at sufficiently small scales, but the onset for such failure is different for the two forms of matter. Moreover, when the no-slip, quasiequilibrium Navier–Stokes system is no longer applicable, the alternative modeling schemes are different for gases and liquids. For dilute gases, statistical methods are applied and the Boltzmann equation is the cornerstone of such approaches. For liquid flows, the dense nature of the matter precludes the use of the kinetic theory of gases, and numerically intensive molecular dynamics simulations are the only alternative rooted in first principles. The present paper discusses the above issues as well as outlines physical phenomena unique to liquid flows in minute devices.
Droplet formation and ejection from a micromachined ultrasonic droplet generator: Visualization and scaling
Authors: Meacham J. M. , Varady M. J. , Degertekin F. L. , Fedorov A. G.
Published: September 2005

Visualization and scaling of drop-on-demand and continuous-jet fluid atomization of water are presented to elucidate the fluid physics of the ejection process and characterize the modes of operation of a novel micromachined ultrasonic droplet generator. The device comprises a fluid reservoir that is formed between a bulk ceramic piezoelectric transducer and an array of liquid horn structures wet etched into (100) silicon. At resonance, the transducer generates a standing ultrasonic pressure wave within the cavity and the wave is focused at the tip of the nozzle by the horn structure. Device operation has been demonstrated by water droplet ejection from 5to10μm orifices at multiple resonant frequencies between 1 and 5MHz. The intimate interactions between focused ultrasonic pressure waves and capillary waves formed at the liquid–air interface located at the nozzle tip are found to govern the ejection dynamics, leading to different ejection modalities ranging from individual droplets to continuous jet. Specifically, we report the results of high-resolution stroboscopic optical imaging of the liquid–air interface evolution during acoustic pumping to elucidate the role of capillary waves in the droplet formation and ejection process. A basic understanding of the governing physics gained through careful visualization and scaling forms the basis for development of improved theoretical models for the droplet formation and ejection processes by accounting for key fluid mechanical features of the phenomena.
Transient micromixing: Examples of laminar and chaotic stirring
Authors: Gleeson James P.
Published: September 2005

The efficiency of a micromixing device may be quantified by the time taken for a given initial state of separated fluids to reach a desired level of homogenization. In the physically relevant case of high Peclet number the accurate prediction of the mixing time is a challenging problem, even in simple two-dimensional flows within bounded domains. In this paper a closed-form solution for the time dependence of mixing in an annular micromixer is derived and verified by numerical simulation. The mixing time is found to scale with Peclet number as a power law, but the power-law exponent depends on the level of homogeneity desired in the final state. Numerical simulation of a recent model of chaotic mixing reveals a vortexlike stirring effect in quasiperiodic islands of the Poincaré map of the flow, which strongly influences the mixing time. This stirring effect is identified with an exponential decrease in solute variance on an intermediate time scale, being subdominant to the asymptotic long-time decay, but sensitive to the initial loading of fluids in the mixer. The subdominant decay rate is calculated to scale with Peclet number as the square root of the dominant decay rate.
Current and current fluctuations in quantum shuttles
Authors: Jauho Antti-Pekka , Flindt Christian , Novotný Tomáš , Donarini Andrea
Published: September 2005

We review the properties of electron shuttles, i.e., nanoelectromechanical devices that transport electrons one by one by utilizing a combination of electronic and mechanical degrees of freedom. We focus on the extreme quantum limit, where the mechanical motion is quantized. We introduce the main theoretical tools needed for the analysis, e.g., generalized master equations and Wigner functions, and we outline the methods how the resulting large numerical problems can be handled. Illustrative results are given for current, noise, and full counting statistics for a number of model systems. Throughout the review we focus on the physics behind the various approximations, and some simple examples are given to illustrate the theoretical concepts. We also comment on the experimental situation.
Electron vortices in semiconductors devices
Authors: Mohseni Kamran , Shakouri Ali , Ram Rajeev J. , Abraham Mathew C.
Published: September 2005

The hydrodynamic model of electron transport in semiconductors is analyzed and, in analogy with vortices in fluid mechanics, the curl of electron velocity is defined as electron vorticity, and the transport equation for the electron vorticity is derived. Aside from the classical hydrodynamic sources of vorticity, collision terms in the continuity and momentum equations are identified as sources and sinks of electron vorticity. Similar to three-dimensional fluid flows there is a vortex stretching term in the vorticity equation. This term could be responsible for the possible cascade of electron kinetic energy to small scales and formation of chaotic turbulent electron transport regimes. A scale analysis of the electron vorticity equation is performed and the relative order of magnitude of each sources of vorticity is found. This analysis and the calculation of electron mean-free-path due to electron–electron and electron–phonon scatterings characterize a transport regime with significant electron vorticity effects. Furthermore, conditions for observation of electron vortices in semiconductor devices are predicted.