bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of ovule abortion in self‐incompatible and self‐fertile lines of white clover (Trifolium repens L.)
Authors: MARSHALL A H , COWAN A A , MICHAELSON‐YEATES T P T
Published: February 2008

Plants of white clover (Trifolium repens L.) cv. Olwen and three genotypes of each of three self‐fertile inbred lines of white clover were grown from seed in a bee‐proof glasshouse. When in flower, a series of crosses within and between the self‐incompatible (SI) and self‐fertile (SF) lines was made and ovule growth and seed production measured 7 and 28 days after pollination (DAP) respectively. At harvest, the SF plants had a lower proportion of ovules aborting and more seeds per floret than the SI plants, though the mean seed weight of the SI plants was greater. Ovule abortion was observed in both the SF and SI plants though the number of aborted ovules was greater in the SI plants. The stage when abortion occurred also differed. All of the ovule abortion in the SI plants occurred within a 7‐day period after pollination. In the SF plants, some abortion was observed in this period but also between 7 and 28 DAP, when the seed was harvested. This suggested that abortion, up to 7 DAP, is due primarily to genetic factors whilst subsequent abortion, between 7 and 28 DAP, is due to non‐genetic factors.
Variation in the glucosinolate content of vegetative tissues of Chinese lines of Brassica napus L
Authors: LI YUNCHANG , KIDDLE GUY , BENNETT RICHARD , DOUGHTY KEVIN , WALLSGROVE ROGER
Published: February 2008

The glucosinolate content of leaves, stems and roots of a range of Chinese oilseed rape (Brassica napus L.) breeding lines was analysed. Total content and spectrum of individual glucosinolates varied widely, and there was no correlation between seed and vegetative tissue glucosinolate content. Lines with low seed glucosinolates (00) did not necessarily have low glucosinolate content in vegetative tissues; nor did high seed glucosinolate lines always have high vegetative tissue content. There was no correlation between the glucosinolate content of leaf, stem, and root in any given line. It appears that glucosinolate synthesis and accumulation is under tissue‐specific control, and the mutation which blocks accumulation of glucosinolates in seeds does not influence other tissues. The responses of these lines to elicitors was also examined. Methyl jasmonate and salicylic acid treatments produced increases in leaf indolyl and aromatic glucosinolates respectively. However, the extent of such increases differed widely between the lines, and there were other, less consistent, effects on other classes of glucosinolate. There seems to be greater variation in glucosinolate accumulation in rape than has previously been reported, and the lines described here have considerable potential for evaluating the effects of manipulating glucosinolate profiles on pest and disease interactions.
The role of leaf wounding and an epigeal predator on caterpillar damage to tomato plants
Authors: HODGE SIMON , WRATTEN STEVE , SMITH JASON , THOMAS MATHEW , FRAMPTON CHRIS
Published: February 2008

The effects of leaf wounding and the presence of a New Zealand carabid predator, Megadromus antarcticus, on the mortality of, and leaf damage caused by, Spodoptera litura on tomatoes were examined in glass houses. The presence of the non‐climbing carabid increased S. litura mortality with a subsequent decrease in leaf damage. Leaf wounding produced a possible decrease in herbivory but did not affect S. litura mortality. Neither leaf wounding or the presence of carabids affected the vertical distribution of leaf damage on the tomato plants. The role of M. antarcticus as a biocontrol agent for tomato pests in New Zealand is briefly discussed.
Effects of carbaryl and cyhexatin on survival and reproductive behaviour of Cydia pomonella (Lepidoptera: Tortricidae)
Authors: ABIVARDI CYRUS , WEBER DONALD C , DORN SILVIA
Published: February 2008

The effects of carbaryl, an insecticide and an abscission agent, and cyhexatin, an acaricide, on the survival, reproductive behaviour and subsequent egg hatch and larval migration of the codling moth, Cydia pomonella L., were investigated under laboratory conditions. Dilution series starting with the concentration recommended for high volume application in the field were evenly sprayed in plastic cups. Depending on the concentration used, both pesticides resulted in high adult mortality, males being more susceptible. Although the total number of the eggs laid by C. pomonella females was significantly reduced in most treatments, the females exposed to different residues of carbaryl laid significantly more eggs during the first 24 h of exposure. This was not the case for cyhexatin.

While in all treatments almost 50% of the eggs were laid on the side of the cups, the spatial distribution of the eggs laid under the lid and on the floor was concentration dependent. With one exception, continuous exposure of the moths to carbaryl significantly reduced the number of spermatophores per female. Less than one spermatophore per female was transferred at the highest four concentrations of carbaryl and the highest three concentrations of cyhexatin; whereas, the number of spermatophores per female amounted to about four per female for the other treatments. In contrast to carbaryl, which exhibited a high ovicidal effect at all concentrations, the ovicidal activity of cyhexatin was low. This was manifested in a high rate of egg hatch and the extent of embryonic development in most of the treatments. Furthermore, while carbaryl killed the newly‐hatched larvae at all concentrations, cyhexatin acted as a larvicide at the highest two concentrations only.
Evaluation of micropropagated plantain and banana (Musa spp.) for banana streak badnavirus incidence under field and screenhouse conditions in Nigeria
Authors: DAHAL G. , GAUHL F. , PASBERG‐GAUHL C. , HUGHES J d'A , THOTTAPPILLY G. , LOCKHART B E L
Published: February 2008

Between 1991 to 1996, more than 50 Musa hybrids and 10 landraces were evaluated under field and screenhouse conditions for virus symptoms resembling those caused by banana streak badnavirus (BSV). The symptoms included chlorotic streaks, leaf deformation, stunting, cigar leaf death, distortion of the peduncle, bunch or fruits, and internal pseudostem necrosis. Immunosorbent electron microscopy (ISEM) of randomly selected plants with one or more of these symptoms confirmed the presence of BSV particles in 15 tropical Musa plantain hybrids (TMPx) and five Musa landraces. Under both field and screenhouse conditions, the incidence of symptomatic plants in the hybrids was significantly higher than in the landraces. The hybrids also generally had a higher concentration of BSV antigens, as determined by enzyme‐linked immunosorbent assay (ELISA). By contrast, most BSV‐infected landraces were symptomless and had very low or undetectable amounts of BSV antigens. There was a significant variation in incidence of symptomatic plants between genotypes, experiments and year of observation. These results are discussed in relation to the higher natural BSV incidence observed on some Musa hybrids as compared with their parental genotypes.
Supplementary foliar N, P and K, applied individually or in combinations, and the tolerance of potatoes to infection by the potato cyst nematodes Globodera rostochiensis and G. pallida
Authors: GROVE I G , HAYDOCK P P J , EVANS K. , LEWIS D J
Published: February 2008

The use of supplementary foliar N, P and K to ameliorate the reduced nutrient uptake of potato plants infected by potato cyst nematode (PCN) were investigated. The potato cv. Pentland Dell achieved yields in plots not treated with oxamyl similar to those found in plots treated with oxamyl when supplementary foliar N or N plus K was applied to plots infested with 13 eggs g‐1 soil of Globodera pallida. Yield improvements from foliar N applications were attributed to increased leaf area index but the reason for yield increases from foliar N plus K applications could not be clarified. In a second experiment, where PCN infestation was 76 eggs g‐l soil, the potato cv. Sante gave yields up to 19% higher than a standard fertiliser practice when supplementary foliar N was applied to plots not treated with oxamyl. Nutrient analysis showed that without oxamyl there were significantly lower concentrations of N, P and K in whole plant dry matter at 58 days after planting (DAP) but higher levels of N in the fourth leaf dry matter at 98 DAP. Emergence was significantly advanced by the use of oxamyl in both experiments. Sante dramatically reduced populations of Globodera rostochiensis from an average of 76 eggs g‐1 soil to 7 eggs g‐1 soil. Foliar application of nutrients is a promising method of ameliorating the effects on potatoes of PCN invasion but the nutrient concentrations and timing of individual sprays need to be more closely matched to crop requirement than was possible in our experiments
An analysis of the variation in crown size in sugar‐beet (Beta vulgaris) grown in England
Authors: MILFORD G F J , HOUGHTON B J
Published: February 2008

The processed part of the sugar‐beet plant, the beet, consists of secondary storage tissues developed from the root and hypocotyl and the crown which, botanically, is the compressed stem. Crowns contain less sugar than roots and higher concentrations of melassigenic substances (such as amino‐nitrogen compounds, sodium, potassium and invert sugars) which impair the crystallisation of white sugar during processing and make beets with high proportions of crown costly to process. Two factors influence the amount of crown material in beet delivered to factories: the original size of the whole crown in intact beet (subsequently referred to as the biological crown), and the fraction removed by the topping mechanisms of beet harvesters when the crop is lifted. The residue left on the delivered beet, for which growers in the UK are not paid, is measured as crown tare at the factory.

To understand the causes of variation in crown tare, an analysis was made of the trend and variation in the size of the biological crown of sugar beet varieties introduced in the UK during the last 25 yr using information from past variety trials and new trials done in 1993, 1997 and 1998. Except for a few diploids, the biological crown was generally as large and variable in recently‐introduced varieties as in those grown 15–20 yr ago. Its size was strongly influenced by locational and seasonal factors which changed the plant's shoot:root ratio primarily, it is suggested, through differences in amounts of available nitrogen. There was no evidence of changes in beet anatomy in recently‐introduced varieties that would result in root material being removed with the crown when samples of delivered, machine‐topped beet are contractually de‐crowned to estimate crown tares in the factory tarehouse.

Variable amounts of crown are removed by harvesting machines. Experiments showed that a greater proportion of beet were over‐topped and more root material was removed with the crown when the biological crown was small and when harvester knives were set low to deliver a minimal crown tare. In these situations, significant amounts of root material, for which growers would be paid if delivered to the factory, were left in the field. Data from differential machine‐topping trials on commercial sugar beet crops at four locations in 1996 and 1997 were used to relate yield loss through over‐topping to crown tare. A crown tare of at least 8% was needed to ensure that no economic yield was left in the field; below this level the losses in delivered yield and grower's income increased exponentially through over‐topping. It was estimated from the factory records of individual contracts that deliveries of beet with crown tares below 8% decreased the national adjusted yield of clean beet by 58 400 t in 1997, equivalent to 0.34 t ha‐1 and 0.56% of the total delivered tonnage.
The aggregative numerical response of polyphagous predators to aphids in cereal fields: attraction to what?
Authors: MONSRUD CARSTEN , TOFT SØREN
Published: February 2008

We tested in a field experiment two hypotheses for why polyphagous predators aggregate at concentrations of aphids: 1) because they are attracted directly to aphids as prey, or 2) because they are attracted to alternative prey that aggregate around the honeydew produced by aphids. Small plots were established in the field with two experimental treatments, aphid addition and honey spraying, and a watersprayed control, each replicated 10 times. Arthropods were recorded by pitfall traps and sticky traps in each plot. Diptera were significantly more abundant in the honey plots. Of the predators,Agonum dorsale, “All carabids” andPhilonthussp. were most abundant in the honey plots;Tachyporusspp. and carabid and staphylinid larvae were most abundant in the aphid addition plots. It is suggested that these results reflect differences among the predators in their ability to tolerate and utilise aphids as food.
Effects of infection time and moisture on development of ear blight and deoxynivalenol production by Fusarium spp. in wheat
Authors: LACEY J. , BATEMAN G L , MIROCHA C J
Published: February 2008

Wheat ears were inoculated with conidia of Fusarium spp. at different growth stages between ear emergence and harvest and moist conditions were maintained for up to 7 days subsequently by mist irrigation. Of the fungi tested (Fusarium culmorum, F. avenaceum, F. tricinctum, F. sporotrichioides and Microdochium nivale), only F. culmorum produced ear blight symptoms and grain samples were found subsequently to contain deoxynivalenol. Most ear infection and deoxynivalenol formation occurred following inoculation at about mid‐anthesis. Small amounts of deoxynivalenol were formed and some F. culmorum was isolated even in the absence of ear blight symptoms. An overnight wet period was sufficient to initiate infection and deoxynivalenol formation but both were increased by extending the wet period up to at least 3 days. Recovery of Fusarium spp. from harvested grain was usually possible whether or not symptoms developed. F. culmorum usually persisted and often increased to moderately high levels after storage for 7 wk in a range of moisture conditions.
Weed vegetation (wild flora) of long established organic versus conventional cereal fields in Denmark
Authors: HALD A B
Published: February 2008

The vegetation of weeds was sampled in matched pairs of long established organic and contemporary conventional cereal fields in summer 1987, and in spring and summer 1988, with an extended Raunkiaer circle at distances up to 50 m from the field boundary. In spring 1988, the number of plants were also counted. Species density, plant density, a proxy measure of plant density (accumulated Frequency Sum), crop and weed biomass, and occurrence of plants assigned to functional groups, are compared between farming systems. The plants were assigned to functional groups according to: (i) herbivore associations to broad‐leaved taxa and (ii) flower location in the canopy, i.e. visibility and availability to flying insects. Furthermore, crop margin and mid‐field were compared concerning species density and accumulated Frequency Sum.

All variables that differed among the two farming systems had highest values ‐ often several times higher ‐ in the organic system with four exceptions: total biomass, biomass of crop, proportion of a single broad‐leaved taxon and of grasses. The differences between the two systems were largest mid‐field due to a pronounced pre‐herbicide spraying gradient in species and plant density from crop margin to mid‐field in conventional fields. A similar gradient was not found in the organic fields.
The critical weed‐free period in organically‐grown winter wheat
Authors: WELSH J P , BULSON H A J , STOPES C E , FROUD‐WILLIAMS R J , MURDOCH A J
Published: February 2008

Two experiments were conducted in central southern England between September 1994 and August 1996 to identify the critical weed‐free period in organically grown winter wheat (Triticum aestivum, cv. Mercia). In competition with a mixed weed infestation of predominatelyAlopecurus myosuroidesandTripleurospermum inodorumit was found that wheat yield decreased as the duration of the weed‐infested period increased and that the crop needed to be kept free of weeds from sowing in order to completely avoid any yield loss. Also, weeds emerging in the wheat crop (predominatelyT. inodorum) during the growing season had a significant and detrimental effect on yield. The existence of the critical period, therefore, depends on the imposition of an acceptable yield loss. If a 5% yield loss gives a marginal benefit compared with the cost of weed control, the critical period will begin at 506°C days after sowing (November) and end at 1023°C days after sowing (February). This information could be used by farmers to target mechanical weeding operations to control weeds at a time that will have maximum benefit to the crop.
A thermal time model of post‐initiation flower development in the shade plant, cineraria
Authors: YEH D M , ATHERTON J G , CRAIGON J.
Published: February 2008

Effects of temperature on flower development in cineraria cv. Cindy Blue were studied in controlled environment rooms and in glasshouses. The base, optimum and maximum temperatures respectively for progress to macroscopic flower appearance after flower initiation respectively were 1.6°C, 19.3°C and 39.8°C. From these cardinal temperatures, a thermal time requirement for flower appearance after flower initiation was calculated to be 130°Cd. The base, optimum and maximum temperatures for progress to anthesis after flower initiation were respectively 1.7°C, 22.3°C and 37.1°C and from these values, the thermal time required to reach anthesis after flower initiation was calculated to be 555°Cd. No significant difference was demonstrated between thermal times for flower development in plants grown in controlled environment growth rooms or under glasshouse conditions where irradiance and photoperiod varied markedly.
Still there's no food! Food insecurity in a refugee population in Perth, Western Australia
Authors: GALLEGOS Danielle , ELLIES Pernilla , WRIGHT Janine
Published: February 2008

Aim:  To identify food insecurity and examine its association with socio‐demographic factors in a group of newly arrived refugees.

Methods:  Structured questionnaire based around the same question asked during the National Nutrition Survey (1995). The questionnaire was administered to a service‐based sample of clients accessing early intervention services. Fifty‐one individuals who were newly arrived refugees, resident in Australia for less than 12 months and who were receiving torture and trauma counselling.

Results:  Thirty‐six individuals (71% of sample) reported running out of food. This percentage was much greater than the 5.2% recorded across all social and economic groups in the 1995 National Nutrition Survey. The most common reasons for running out of food were related to large household bills, late welfare payments, poor household skills, sending money ‘home’, transport issues and poor budgeting skills.

Conclusion:  Food insecurity in refugees in Perth, Western Australia is comparable to the rates of food insecurity found in this population in other parts of the developed world. There are, however, significant ramifications for the development of intervention strategies as well as policy implications. For refugees, focusing on community food security strategies will assist in building community capacity, facilitate the retention of cultural integrity, restore and maintain dignity, and will be instrumental in ensuring both short‐ and long‐term health.
Meal and food preferences of nutritionally at‐risk inpatients admitted to two Australian tertiary teaching hospitals
Authors: VIVANTI Angela , BANKS Merrilyn , ALIAKBARI Judith , SUTER Michelle , HANNAN‐JONES Mary , MCBRIDE Elizabeth
Published: February 2008

Aim:  To determine preferences for meals and snack of long‐stay patients and hospitalised patients with increased energy and protein requirements.

Methods:  Using consistent methodology across two tertiary teaching hospitals, a convenience sample of adult public hospital inpatients with increased energy and protein requirements or longer stays (seven days or more) were interviewed regarding meal and snack preferences. Descriptive reporting of sample representativeness, preferred foods and frequency of meals and between meal snacks.

Results:  Of 134 respondents, 55% reported a decreased appetite and 28% rated their appetite as ‘poor’. Most felt like eating either nothing (42%) or soup (15%) when unwell. The most desired foods were hot meal items, including eggs (31%), meat dishes (20%) and soup (69%). Of items not routinely available, soft drink (7.6%) and alcohol (6.7%) were most commonly desired during admission. Almost half (49%) reported difficulty opening packaged food and a majority (81%) indicated finger foods were easy to eat.

Conclusion:  Appetites during admission were frequently lower than usual. Responses encourage consideration of eggs, meat dishes and soups for long‐stayers or those with high‐energy, high‐protein needs. Easy to consume but not routinely offered, between meal items, such as soup, juice, cake, soft drink or Milo could be explored further to enhance oral intakes.
Foods, nutrients and portions consumed by a sample of Australian children aged 16–24 months
Authors: WEBB Karen , RUTISHAUSER Ingrid , KNEZEVIC Natalia
Published: February 2008

Aim:  To describe the diet of a sample of Australian children aged 16–24 months with regard to the amounts of foods and nutrients consumed.

Methods:  Cross‐sectional data collected from participants in a five‐year randomised trial of the primary prevention of asthma. Pregnant women with a family history of atopy were recruited from six hospital antenatal clinics in western Sydney. At the 18‐month assessment, carers of 429 of children completed three‐day weighed food records. Three‐day average intakes of foods and nutrients and average portions per eating occasion for commonly consumed foods. T‐tests for comparing gender differences.

Results:  Diets were characterised by large amounts of milk and non‐milk drinks with smaller amounts of cereals, fruits, vegetables and meats. Total energy intake was significantly higher for boys than girls and exceeded estimated energy requirements in both boys and girls. Food groups contributing most to energy included milk and milk products (35%), cereals (15%), cereal‐based products (9%) and non‐milk drinks (8%). Micronutrient intakes were below the Estimated Average Requirement in more than 5% of the children for vitamin A, calcium, vitamin C and iron. Sodium intakes exceeded the upper level of 1000 mg for 62% of children, while dietary fibre intake was only half the Adequate Intake of 14 g. Relatively few foods were widely consumed and median portion sizes were typically small in relation to commonly used reference portion sizes.

Conclusion:  These data may be useful as a preliminary basis for developing age‐specific dietary surveillance tools and dietary guidance for children aged one to two years.
Investigation of the impact of intensive broiler rearing on local fine particulate matter concentrations
Authors: Bull Michael
Published: February 2008

During the review and assessment of air quality process, South Norfolk Council identified that poultry rearing could be a significant source of particulate matter and therefore required more detailed study. Using standard emission data for poultry rearing dispersion modelling confirmed that there was potential for an exceedance of the UK objective for fine particulate matter (PM10). However, it was recognised that the emission data available were based on very limited information and further monitoring was required to investigate the issue fully. Accordingly, an air quality monitoring programme was set up to measure PM10 concentrations around a large broiler‐rearing facility. This used both a TEOM‐ and Partisol‐type instrument to allow direct comparison with the UK objective and to provide continuous results to use with wind direction monitoring to assist in identifying the source of particulate matter in the area. The results from the monitoring showed that an exceedance of the UK objective was unlikely, although the broiler sheds did appear to result in a significant increase in PM10 concentrations in the area, with average concentrations increasing by nearly 12 μg/m3 when the wind direction carried emissions from the sheds to the monitoring site. Given that the test site was located near a very large broiler farm, it was considered that it was unlikely that broiler‐rearing activities would result in an exceedance of the UK objective for PM10.
Managing urban wastewater in China: a survey of build–operate–transfer contracts
Authors: Braadbaart Okke , Zhang Mingshun , Wang Yang
Published: February 2008

This paper reports on a nationwide field survey of wastewater plants under build–operate–transfer (BOT) contracts in China. The survey yielded information on contracting parties, size, duration and location of 37 BOT contracts. The key findings are that municipal governments feature as first parties to BOTs, and that many second parties are domestic rather than international entities. Municipalities favour BOT contracts because of familiarity with infrastructure BOTs and the access they offer to the capital market. A subsample of five BOT contract documents was examined. Gaps in contract specifications included clauses allocating responsibility for defects in plant design and environmental incidents, and coverage of commercial risk. Many of the BOT contracts examined qualify as public–public partnerships rather than public–private partnerships (PPPs) in the classic sense of the word. This dampens the risk of contract failure.
Pathology of peripheral intrahepatic cholangiocarcinoma with reference to tumorigenesis
Authors: Nakanuma Yasuni , Sasaki Motoko , Ikeda Hiroko , Sato Yasunori , Zen Yoh , Kosaka Kazuto , Harada Kenichi
Published: February 2008

Cholangiocarcinomas (CCs) are neoplasms with cholangiocyte differentiation, and may arise from cholangiocytes of the biliary tree and possibly cholangiocyte progenitor cells. Intrahepatic CCs can be divided into the perihilar and peripheral types. Peripheral CCs present grossly as a mass forming tumor, and histologically as an adenocarcinoma of varying shapes and phenotypes. Some peripheral CCs (ductular type) are characterized by: (i) a histological resemblance to reactive bile ductules; (ii) the expression of neural cell adhesion molecule (NCAM) and vimentin. This type shows: (i) grossly, a blurred border; and (ii) histologically, carcinoma cells replacing the adjoining hepatocytes at the border of the tumor. It is frequently associated with neutrophilic infiltration and also with granulocyte and granulocyte macrophage colony‐stimulating factors. We propose to call this type “ductular CC.” The other peripheral CC (duct type) includes ordinary adenocarcinoma with well to moderately differentiated tubular and micropapillary patterns and is negative for NCAM but positive for mucin. This type can be called “duct CC,” and shows a rather compressive growth. Interestingly, CC components of combined hepatocellular CC share the features of ductular CC, suggesting that hepatic progenitor cells may be involved in the tumorigenesis of ductular CC. The biological behavior of ductular CC and duct CC remains obscure, and follow‐up and molecular studies on these tumors are required in order for these two CCs to be recognized as disease entities, and so as to evaluate their carcinogenesis.
Time – size tradeoffs: a phylogenetic comparative study of flowering time, plant height and seed mass in a north‐temperate flora
Authors: Bolmgren Kjell , D. Cowan Peter
Published: February 2008

Parents face a timing problem as to when they should begin devoting resources from their own growth and survival to mating and offspring development. Seed mass and number, as well as maternal survival via plant size, are dependent on time for development. The time available in the favorable season will also affect the size of the developing juveniles and their survival through the unfavorable season. Flowering time may thus represent the outcome of such a time partitioning problem. We analyzed correlations between flowering onset time, seed mass, and plant height in a north‐temperate flora, using both cross‐species comparisons and phylogenetic comparative methods. Among perennial herbs, flowering onset time was negatively correlated with seed mass (i.e. plants with larger seeds started flowering earlier) while flowering onset time was positively correlated with plant height. Neither of these correlations was found among woody plants. Among annual plants, flowering onset time was positively correlated with seed mass. Cross‐species and phylogenetically informed analyses largely agreed, except that flowering onset time was also positively correlated with plant height among annuals in the cross‐species analysis. The different signs of the correlations between flowering onset time and seed mass (compar. gee regression coefficient=−7.8) and flowering onset time and plant height (compar. gee regression coefficient=+30.5) for perennial herbs, indicate that the duration of the growth season may underlie a tradeoff between maternal size and offspring size in perennial herbs, and we discuss how the partitioning of the season between parents and offspring may explain the association between early flowering and larger seed mass among these plants.
Effects of heterogeneous interaction strengths on food web complexity
Authors: Garcia‐Domingo Josep L. , Saldaña Joan
Published: February 2008

Using a bioenergetic model we show that the pattern of foraging preferences greatly determines the complexity of the resulting food webs. By complexity we refer to the degree of richness of food‐web architecture, measured in terms of some topological indicators (number of persistent species and links, connectance, link density, number of trophic levels, and frequency of weak links). The poorest food‐web architecture is found for a mean‐field scenario where all foraging preferences are assumed to be the same. Richer food webs appear when foraging preferences depend on the trophic position of species. Food‐web complexity increases with the number of basal species. We also find a strong correlation between the complexity of a trophic module and the complexity of entire food webs with the same pattern of foraging preferences.
Do lizard communities partition the trophic niche? A worldwide meta‐analysis using null models
Authors: Luiselli Luca
Published: February 2008

Lizards have been widely used as model organisms in community ecology over the past 30 years. I have reviewed more than 50 studies from the literature on the community ecology of lizards worldwide, with a focus on studies from 1990–2007. I determined if there is support for the hypotheses that many lizard communities 1) are non‐randomly organized along the trophic niche dimension, and 2) partition the available food resource to minimize interspecific competition. I used data on number of prey items and percentage of prey volume, to calculate dietary overlap among species. I compared true datasets to randomly generate new datasets produced by 3×104 Monte Carlo permutations using two algorithms (RA2 and RA3). The great majority (more than 80%) of the communities were randomly organized along the trophic niche dimension using RA2 or RA3; the frequency of occurrence of detecting a non‐random structure in lizard community dietary studies did not differ significantly between datasets based on either number of prey items or prey volume. Thus, lizard communities usually do not partition the trophic niche axis. Concerning the number of prey items, logistic regression models showed that the presence of a structure in the dataset did not depend on number of species, method employed to obtain dietary data, matrix size, or location (continent), but instead significantly depended on whether a community was tropical. Concerning prey volume, presence of a structure in the dataset also did not depend on number of species, method employed to obtain dietary data, and tropical vs non‐tropical origin, but was marginally dependent on continent (South America was favoured for identifying a structure in the dataset) and matrix size. In general, a structure in the dataset was more often uncovered by using RA2 than RA3. Overall, I conclude that 1) lizard communities are unlikely to partition available food resources, and 2) as the method for identifying dietary items does not allow for accurate prey identification (at least at the genus level), there is a risk of obtaining false null results about community structure. This is because structure along the trophic niche axis is genuinely rare in lizards and also because inappropriate methods may erroneously lead to this conclusion. Therefore, conclusions from studies utilizing stomach dissection as a source of diet data (still common in the literature) should be cautiously considered for ethical reasons and because it is difficult to find any difference between stomach‐dissection and fecal‐pellet data when assessing the presence of a structure in datasets. My data also showed there are minor differences in the probability of detecting a structure in datasets using prey item number or prey volume data for lizards. The biases, both statistical and biological, associated with this meta‐analysis are discussed.
Agricultural landscapes with organic crops support higher pollinator diversity
Authors: Holzschuh Andrea , Steffan‐Dewenter Ingolf , Tscharntke Teja
Published: February 2008

Pollinators are traditionally thought to perceive non‐flowering crop fields as hostile landscape matrix. In this study, we show that landscapes composed of higher proportions of organic crop fields support more bee species at greater abundances in fallow strips. An increase in organic cropping in the surrounding landscape from 5% to 20% enhanced bee species richness in fallow strips by 50%, density of solitary bees by 60% and bumble bee density by 150%. Bee species richness and bumble bee density responded strongest to organic cropping in landscape sectors with 500 m radius, solitary bee density in landscape sectors with 250 m radius. The most likely source of these results is that crop and noncrop habitats are strongly connected via bee foraging at the landscape scale. It seems likely that bees depending on nesting sites in fallow strips benefited from the more abundant flower resources provided by broadleaved weeds in organic crop fields. We conclude that the incorporation of organic crop fields into conventionally managed agricultural landscapes can provide food resources needed to sustain greater pollinator species richness in noncrop habitats.
The evolution of ecological specialization in southern African ungulates: competition‐ or physical environmental turnover?
Authors: Codron Daryl , Brink James S. , Rossouw Lloyd , Clauss Marcus
Published: February 2008

Using long‐term diet reconstructions spanning the past one million years, we contrast hypotheses that biotic interactions versus physical environmental changes are primary drivers of evolutionary turnover in mammals. We use stable carbon (δ13C) and oxygen (δ18O) isotope ratios in tooth enamel carbonate to trace herbivore niche shifts through the Late Quaternary Land Mammal Ages (LMAs) of grassland savannas in the South African interior (Cornelian‐1.0 to 0.6 Ma; Florisian‐500 to 10 ka; and Holocene/modern). Data reveal niche separation amongst closely related coeval taxa, and dispersals through time into empty niche spaces following extinctions. This suggests a primary role of competitive exclusion and niche displacement for speciation and extinctions in these early grassland environments. However, niche changes through time show a similar trend in many taxa, entailing increased δ13C (elevated C4 grass consumption) from the Cornelian to the Florisian, and from the Florisian to the Holocene/modern, and elevated δ18O in Holocene/modern taxa that reflect global aridification around the terminal Pleistocene. Commonality in isotopic trends implies universal environmental forcing of ecological, and ultimately macroevolutionary, turnover. Yet some taxa shift from a mixed C3/C4 diet in the Florisian to a near‐pure C3 diet today. Indeed, we find that while δ13C data are normally distributed for Cornelian fossils, non‐normal distributions characterize more recent time intervals. Such distributions are in line with the bimodal distribution of δ13C and diet in contemporary African ungulates. Thus, while environmental forcing did not, by necessity, lead to increases in C4 intake, the results show changes from mixed to more specialized diets. We propose that this niche specialization was a function of long‐term exposure to C4 grasslands, consistent with predictions that relatively high metabolic demands of C4 grazing in subtropical environments forced the differentiation of herbivores into one of two highly specialized feeding niches, i.e. C3 browsing or C4 grazing.
Epigenetic effects of infection on the phenotype of host offspring: parasites reaching across host generations
Authors: Poulin Robert , Thomas Frédéric
Published: February 2008

Parasite‐induced changes in host phenotype are now well‐documented from a wide range of taxa. There is a growing body of evidence indicating that parasites can also have trans‐generational consequences, with infection of a host leading to changes in the phenotype of its offspring, though the latter are not parasitised. Several proximate mechanisms have been put forward to explain these ‘maternal’ effects, most involving hormonal or other physiological pathways, ultimately leading to offspring that are pre‐adapted to the parasites they are most likely to encounter based on their mother's experience. Here, we propose that all these trans‐generational effects on offspring phenotype must involve epigenetic phenomena. Epigenetics concerns the appearance and inheritance of seemingly new phenotypic traits without changes in the underlying DNA sequence. Since diet and other environmental factors experienced by a mother can affect gene expression in her offspring by turning genes ‘on’ or ‘off’ (for example, via DNA methylation), why couldn't parasites do it? Although epigenetic effects have not been explicitly invoked to account for trans‐generational impacts of parasites on the phenotype of host offspring, the existing evidence is fully compatible with their involvement. We argue that epigenetic mechanisms must play a central role; we also discuss their evolutionary implications and suggest questions for future investigations in this new and exciting research direction.
Algorithm for Multiple Disassembly and Parallel Assemblies
Authors: Dutta D. , Woo T. C.
Published: February 2008

We consider the geometric problem of generating efficient sequences for disassembling components. First, a classification of assemblies is proposed based on logical, dimensional and geometric complexities, and a simple method is outlined for recognizing parallel and sequential assemblies. Next, an efficient algorithm is outlined for removing multiple components from an assembly. Finally, we consider parallel assemblies and outline two algorithms for their disassembly.
A Computer Controlled Contouring Twist Drill Grinding Machine
Authors: Vangsness J. D. , Fugelso M. A.
Published: February 2008

This paper describes a computer controlled twist drill grinding machine that places a maximum of function in the computer controller making the mechanical part of the machine very simple. A wide variety of conical points can be produced by a virtual rotation about the cone axis accomplished by simultaneous movement of the grinding machine joints.
Determination of the Load Distribution in a Threaded Connector Having Dissimilar Materials and Varying Thread Stiffness
Authors: Wang W. , Marshek K. M.
Published: February 2008

A modified spring model was developed to predict the load distribution in the threaded portion of a connector. Distinction was made between a compression case (nut and bolt) and a tension case (turnbuckle). The load distribution was described using simple second-order difference equations. Three different nut and bolt (turnbuckle) combinations were discussed: (1) threads of similar materials and geometry, (2) threads of similar geometry but different modulus of elasticity, and (3) threads with varying stiffness.
Designing Multiple-Load Automated Guided Vehicle Systems for Delivering Material from a Central Depot
Authors: Johnson M. Eric , Brandeau Margaret L.
Published: February 2008

We develop and illustrate an approach for design of shop floor automated guided vehicle systems (AGVSs) with multiple-load capacity. Vehicles provide material from a central depot to shop floor workcenters. The AGVS supplements an existing nonautomated material handling system. The design decision is to determine which workstations to service by the AGVS, and how many vehicles are needed, to meet a specified service level. We build upon an existing AGVS design model (a mathematical program) which assumes that vehicles visit workstations on a first-come-first-served basis, carrying one load per trip. We show how that model can be adapted to solve a design problem in which vehicles can carry more than one load per trip—yielding an improved system design. We illustrate our approach by solving six examples inspired by design problems faced at Hewlett-Packard Company.
Analysis of Energy Partition in Grinding
Authors: Guo C. , Malkin S.
Published: February 2008

An analysis is presented for the fraction of the energy transported as heat to the workpiece during grinding. The abrasive grains and grinding fluid in the wheel pores are considered as a thermal composite which moves relative to the grinding zone at the wheel speed. The energy partition fraction to the workpiece is modeled by setting the temperature of the workpiece surface equal to that of the composite surface at every point along the grinding zone, which allows variation of the energy partition along the grinding zone. Analytical results indicate that the energy partition fraction to the workpiece is approximately constant along the grinding zone for regular down grinding, but varies greatly along the grinding zone for regular up grinding and both up and down creep-feed grinding. The resulting temperature distributions have important implications for selecting up versus down grinding especially for creep-feed operations.
Built-up Edge Elimination in Mirror Cutting of Hardened Steel
Authors: Oishi K.
Published: February 2008

A built-up edge will normally give a poor finish. The conventional way of eliminating the built-up edge is to increase cutting speed and feed (i.e., increase tool face temperature). It is shown here that a built-up edge can also be eliminated if the workpiece hardness is above a critical value. This critical value is such that the workpiece hardness be somewhat greater than half the hardness of the built-up edge that forms at low hardness and speed, since the built-up edge hardness is between 2 and 3 times the corresponding workpiece hardness. It is suggested the reason for this is that the hardness of the workpiece must be less than the hardness of the built-up edge, otherwise the built-up edge disappears. This new method of eliminating the built-up edge by use of hard work material prevents built-up edge formation even at low feeds and speeds, thus making it possible to produce extremely a good (mirror) finish under these conditions.
Studies on Double-Side Shearing with Parallel and Straight Cutting Edges (Prevention of Tool Breakage by Bevelled Punches with High Slenderness Ratio)
Authors: Mekaru S. , Fukumoto I. , Makishi T.
Published: February 2008

In the present investigation the cutting edge of a slender punch was bevelled in an attempt to prevent bending or breakage in use. Tests with Kovar sheet showed that use of a bevelled punch significantly reduces the risk of bending or breakage, a particular problem when clearance on both sides of the punch is unbalanced. This is because the punch guides itself in the later stage of the stroke. Tool life tests shearing Kovar sheet with the bevelled punch produced a smaller burr on the product than with the conventional punch. The application of such punches is found to be most suitable for thin materials such as are used in the manufacture of IC and LSI parts.
Morphology of Surfaces Generated by Circular Wire Brushes
Authors: Stango R. J. , Fournelle R. A. , Chada S.
Published: February 2008

The characteristic surface that is generated during orthogonal wire brushing of a flat 6061-T6 aluminum workpart is examined in this paper. Scanning electron microscopy is used for characterizing the surface topography, whereas subsurface microstructure and properties of the brushed region are evaluated by both metallography and microhardness measurements. The unique topographical characteristics of the contact zone suggest material removal and subsequent redeposition onto the workpart. On the basis of the experimental observations, a qualitative theory is advanced which identifies transfer mechanisms for removal and redeposition of aluminum alloy.
Energy Partition to the Workpiece for Grinding with Aluminum Oxide and CBN Abrasive Wheels
Authors: Kohli S. , Guo C. , Malkin S.
Published: February 2008

An experimental investigation is reported of the energy partition to the workpiece for grinding of steels with aluminum oxide and cubic boron nitride (CBN) abrasive wheels. The energy input to the workpiece was obtained by measuring the temperature distribution in the workpiece using an embedded thermocouple technique and matching the results with analytically computed values. It was found that 60-75 percent of the grinding energy is transported to the workpiece as heat with an aluminum oxide abrasive wheel, as compared to only about 20 percent with CBN wheels. An analysis of the results indicates that the much lower energy partition to the workpiece with CBN can be attributed to its very high thermal conductivity whereby a significant portion of the grinding heat is transported to the abrasive instead of to the workpiece. The much lower energy partition to the workpiece with CBN wheels results in much lower grinding temperatures and a greatly reduced tendency for thermal damage to the workpiece.
Sensing and Control of Weld Pool Geometry for Automated GTA Welding
Authors: Kovacevic R. , Zhang Y. M. , Ruan S.
Published: February 2008

Weld pool geometry is a crucial factor in determining welding quality, especially in the case of sheet welding. Its feedback control should be a fundamental requirement for automated welding. However, the real-time precise measurement of pool geometry is a difficult procedure. It has been shown that vision sensing is a promising approach for monitoring the weld pool geometry. Quality images that can be processed in real-time to detect the pool geometry are acquired by using a high shutter speed camera assisted with nitrogen laser as an illumination source. However, during practical welding, impurities or oxides existing on the pool surface complicate image processing. The image features are analyzed and utilized for effectively processing the image. It is shown that the proposed algorithm can always detect the pool boundary with sufficient accuracy in less than 100 ms. Based on this measuring technique, a robust adaptive system has been developed to control the pool area. Experiments show that the proposed control system can overcome the influence caused by various disturbances.
Reason Maintenance in Product Modeling
Authors: Vujosevic R. , Kusiak A. , Szczerbicki E.
Published: February 2008

An approach to product modeling by using a reason maintenance system to reduce the amount of search required for the identification of feasible designs is described. An assumption-based truth maintenance system and multiple worlds are used to discover and store information about feasible designs and to avoid further consideration of infeasible design alternatives. An object-oriented computer program for product modeling is presented.