A reversible, unidirectional molecular rotary motor driven by chemical energy

With the long-term goal of producing nanometer-scale machines, we describe here the unidirectional rotary motion of a synthetic molecular structure fueled by chemical conversions. The basis of the rotation is the movement of a phenyl rotor relative to a naphthyl stator about a single bond axle. The sense of rotation is governed by the choice of chemical reagents that power the motor through four chemically distinct stations. Within the stations, the rotor is held in place by structural features that limit the extent of the rotor's Brownian motion relative to the stator.     

Estimating incidental takes of shearwaters in driftnet fisheries: lessons for the conservation of seabirds

We consider estimation of the magnitude of incidental fisheries ‘bycatch’ for two petrel species, sooty shearwaters (Puffinus griseus) and short-tailed shearwaters (Puffinus tenuirostris). There are clear statistical advantages in estimating bycatch for abundant species such as these, and our results may also guide the conservation and management of rarer species. We used fisheries statistics and observer data to estimate retrospectively the total numbers of sooty and short-tailed shearwaters bycatch in seven large-scale pelagic North Pacific driftnet fisheries between 1952 and 2001. Sensitivity analysis greatly simplified estimation of uncertainty by identifying four driftnet fisheries to be of particular importance in determining the magnitude and precision of the estimated bycatch totals. We estimated that between 1.0 and 12.8 million (95% CI) sooty shearwaters were killed by driftnets between 1952 and 2001. For short-tailed shearwaters we estimated between 4.6 and 21.2 million (95% CI) over the same period. More precise estimation was hampered by the paucity of available observer data, lack of reported detail and inconsistencies among data sources. Estimates may be strongly biased because some dead birds are misidentified or drop out of nets before hauling, or because some records were of live captures that were subsequently released. Improved estimation of overall take and its impact on populations of seabirds requires standardisation of reporting, allowance for potential sampling bias, as well as a clearer definition of the sampling unit and underlying bycatch probability distribution model, and knowledge of potential compensatory changes in population parameters.     

The dynamics of lucerne (Medicago sativa L.) yield components in response to defoliation frequency

The productive life of lucerne (Medicago sativa L.) stands depends on the rate of mortality of individual plants. However, self-thinning of plant populations may be compensated for by increases in other yield components, namely shoots/plant and individual shoot mass. Frequent defoliation reduces lucerne yield but it is unclear whether this is caused by an acceleration of plant mortality or changes in these other yield components. To investigate this, crops with contrasting shoot yields were created using constant 28 or 42-day regrowth cycles applied to a ‘Kaituna’ lucerne crop in Canterbury, New Zealand during the 2002/2003 and 2003/2004 growth seasons. Two further treatments switched from 28 to 42 or 42 to 28 days grazing frequency in mid-summer (4th February) of each year. The annual yield of shoot dry matter (DM) ranged from 12 to 23 t/ha for the treatments defoliated consistently each 28 or 42 days, respectively. Plant population was unaffected by treatments and declined exponentially from 130 plants/m² in June 2002 to 60 plants/m² in September 2004. The dynamics of plant and shoot population were associated with the light environment at the base of the canopy. The slope of the size/density compensation (SDC) of plants was −1.67 for the treatment defoliated each 42 days, near the expected self-thinning slope of −1.5 for stands at constant leaf area index (LAI). Self-thinning of shoots resumed after each defoliation when the LAI reached 2.1 and the transmission of photosynthetically active radiation (PAR_t) was 0.20. At this point the proportion of aerial DM in the tallest (dominant) shoots increased non-linearly from 30 to >80%, due to the mortality of intermediary and suppressed shoots. The average maximum shoot population in each rotation was 780 shoots/m² and unaffected by the decline in plant population due to a compensatory increase from 6 to 13 shoots/plant as the stand thinned. A lower asymptote of 43 plants/m² was estimated as the minimum plant population at which yield component compensation would maintain the productive potential of these ‘Kaituna’ stands. Differences in shoot yield were explained (R² = 0.97) by changes in the individual shoot mass (ISM) that were consistently lowered by frequent defoliation treatments. Frequent defoliations reduced crop productivity by limiting the assimilation of biomass into each individual shoot with negligible impact on shoot appearance rate, the number of shoots per plant at an LAI of 2.1 or the rate of plant population decay. Inter-specific competition for light was proposed as the main factor controlling self-thinning of plants and shoots regardless of their individual C:N status.     

An instrument to monitor infiltration of fine sediment into stable gravel stream beds

An instrument, using a submersible linear displacement transducer mounted beneath a sediment catch-tray, has been developed to monitor infiltration of fine sediment into gravel beds. Field tests show a good correlation between the amount of sediment infiltration into the bed and the total amount of sediment moving through the channel.     

The growth of rainbow trout (Salmo gairdneri) given diets containing chitin and its relationship to chitinolytic enzymes and chitin digestibility

The growth of rainbow trout fed diets containing 4, 10 and 25% chitin, over a 12-week period, was significantly depressed (P < 0.001) when compared with controls fed diets containing 25% starch. There was no difference in growth rate between control fish and those fed diets containing 10% N-acetyl glucosamine (GlcNAc). Isotopically labelled amino sugars were shown to be oxidized when injected intraperitoneally into rainbow trout. Relatively high levels were found of chitinase activity in the stomachs and of chitobiase in the intestines. These enzyme activities were similar in all the trout, irrespective of the amount of chitin in their diets, except that chitobiase in the intestines of fish fed diets containing GlcNAc showed higher levels of activity than the controls (P < 0.05). Chitin was not significantly digested when fed at 10 and 30% of the diet but the apparent digestibility of pre-cooked starch was 50% when fed at either 15 or 25%, on the basis of the inert indicator (Cr₂O₃) method. Chitinase and chitobiase activities were not reduced in fish fed diets containing 10% chitin and an antibiotic (Tribrissen^®) although the alimentary microflora were completely eliminated. Enzyme activities were not enhanced when live chitinolytic bacteria (Vibrio alginolyticus) were incorporated into diets with 10% chitin; these bacteria were only recovered from the intestine. The evidence indicates an endogenous origin of chitinolytic enzymes in the trout gastro-intestinal tract. The presence of either antibiotic or bacteria in the diet had no effect on the digestibility of chitin.     

Seasonal variability in the abundance of Arctic charr (Salvelinus alpinus (L.)) recorded using hydroacoustics in Windermere, UK and its implications for survey design

Abstract –  Hydroacoustic surveys are an important tool for assessing the abundance of Arctic charr ( Salvelinus alpinus (L.)) in lakes, the requirement for which is increasing because of new environmental legislation. Consequently, survey demand is now such that assessments must be undertaken with the minimum of effort compatible with scientific validity. One major complication is seasonal variability in abundance, with which surveyors have attempted to deal by defining somewhat arbitrary seasonal sampling windows. The definition of more objective windows was pursued by analysing variations in the seasonal abundance of Arctic charr in Windermere, UK, recorded using day and night hydroacoustic surveys at monthly intervals from 1991 to 2001. Two alternative sampling windows for night surveys free of significant internal seasonal effects were revealed, i.e., December to September and September to December. It was also found that day surveys gave a useful, although lower, estimate of abundance as compared with night surveys.     

Phytochemical Profile and Antiproliferative Activity of Dough and Bread Fractions Made from Refined and Whole Wheat Flours

Phytochemical profile (phenolic acids, carotenoids, and tocopherols) and antiproliferative properties of bread processing fractions, including the dough, crumb, and upper crust made from refined wheat and whole wheat flours were analyzed for two wheat cultivars. Ferulic acid, lutein, and α‐tocopherol were the predominant phenolic acid, carotenoid, and tocopherol, respectively, extracted from all fractions. The levels of all phytochemicals in whole wheat samples were over eightfold higher than their corresponding refined wheat samples. The concentrations of total phenolic acids (soluble and insoluble bound) were higher in the upper crust of refined (∼60–90%) and whole wheat (∼15–40%) breads than their corresponding dough fractions. However, the dough of whole wheat had higher levels of tocopherols and carotenoids compared with the crumb and upper crust, suggesting that phenolic acids were relatively stable during baking, whereas tocopherols (∼25–80%) and carotenoids (∼20–80%), were partially degraded. The antiproliferative activity of whole wheat bread extracts against HT‐29 cancer cells was weakly correlated with total phenolic acids but showed no correlations with total carotenoid and total tocopherol contents.     

Selected blood chemistry values in mobility-impaired broiler breeder hens with suspected calcium tetany using the i-STAT handheld clinical analyzer

Calcium tetany is a poorly defined disease of broiler breeder hens that results from acute hypocalcemia. It is characterized by impaired mobility, increased mortality, and absence of gross lesions that would explain the impaired mobility. To evaluate if hens with impaired mobility had calcium tetany or other abnormalities, blood values from normal and affected hens were determined using the i-STAT handheld clinical analyzer. Three flocks were evaluated weekly prior to peak production (range 25-30 wk of age) comparing normal hens to hens with clinically apparent calcium tetany. Calcium tetany suspect (CaTS) hens from four additional flocks were also evaluated. Significant hypocalcemia (P < 0.001) was observed in CaTS hens (average = 1.14 mmol/L ionized calcium [iCa]) compared to normal hens (average = 1.53 mmol/L iCa) in only one of three flocks sampled weekly. Clinically affected hens from one of the other four flocks also had hypocalcemia. Blood value abnormalities in mobility-impaired hens without hypocalcemia included hypernatremia. Findings in this study indicate calcium tetany is one cause of impaired mobility in breeder hens, but mobility impairment without hypocalcemia can also occur. Calcium tetany should be confirmed by finding significantly decreased levels of iCa in the blood, as diagnosis based on clinical presentation and necropsy results can be inaccurate. The i-STAT handheld clinical analyzer is an efficient, relatively low-cost method to determine iCa and other blood chemistry values that may be associated with impaired mobility in broiler breeder hens.