6 results
Contributors
-
- By Albert Altchek, David H. Barad, Katharine Batt, Yuval Bdolah, Revaz Botchorishvili, Nicolas Bourdel, Michael S. Broder, Douglas N. Brown, Jubilee Brown, Antoine Maurice Bruhat, Michel Canis, Mine S. Cicek, Carmel J. Cohen, Christopher P. Crum, Christina E. Curtin, Liane Deligdisch, Philip J. Di Saia, Ramez N. Eskander, Tamara Finger, David Fishman, Brooke L. Fridley, David M. Gershenson, Norbert Gleicher, Ellen L. Goode, Pierre S. Gordon, Ioannis Gryparis, Jonathan Hecht, Wendy C. Hsiao, Eric C. Huang, Nathan G. Kase, Valentin Kolev, Lale Kostakoglu, Neri Laufer, Anna Laury, Gerard Mage, Angelica Mareş, Maurie Markman, Luciano G. Nardo, Farr R. Nezhat, Sree Durga Patchava, Tanja Pejovic, Catherine M. Phelan, Benoit Rabischong, Jamal Rahaman, David Rodriguez-Buritica, Paul Saenger, Peter Schlosshauer, William L. Simpson, Cardinale B. Smith, Jason Sternchos
- Edited by Liane Deligdisch, Nathan G. Kase, Carmel J. Cohen
-
- Book:
- Altchek's Diagnosis and Management of Ovarian Disorders
- Published online:
- 05 August 2013
- Print publication:
- 25 July 2013, pp vii-x
-
- Chapter
- Export citation
Growth and yield of winter wheat (Triticum aestivum) crops in response to CO2 and temperature
- T. R. Wheeler, G. R. Batts, R. H. Ellis, P. Hadley, J. I. L. Morison
-
- Journal:
- The Journal of Agricultural Science / Volume 127 / Issue 1 / August 1996
- Published online by Cambridge University Press:
- 27 March 2009, pp. 37-48
-
- Article
- Export citation
-
Crops of winter wheat (Triticum aestivum L. cv. Hereward) were grown within temperature gradient tunnels at a range of temperatures at either c. 350 or 700 μmol mol−1 CO2 in 1991/92 and 1992/93 at Reading, UK. At terminal spikelet stage, leaf area was 45% greater at elevated CO2 in the first year due to more tillers, and was 30% greater in the second year due to larger leaf areas on the primary tillers. At harvest maturity, total crop biomass was negatively related to mean seasonal temperature within each year and CO2 treatment, due principally to shorter crop durations at the warmer temperatures. Biomass was 6–31% greater at elevated compared with normal CO2 and was also affected by a positive interaction between temperature and CO2 in the first year only. Seed yield per unit area was greater at cooler temperatures and at elevated CO2 concentrations. A 7–44% greater seed dry weight at elevated CO2 in the first year was due to more ears per unit area and heavier grains. In the following year, mean seed dry weight was increased by > 72% at elevated CO2, because grain numbers per ear did not decline with an increase in temperature at elevated CO2. Grain numbers were reduced by temperatures > 31 °C immediately before anthesis at normal atmospheric CO2 in 1992/93, and at both CO2 concentrations in 1991/92. To quantify the impact of future climates of elevated CO2 concentrations and warmer temperatures on wheat yields, consideration of both interactions between CO2 and mean seasonal temperature, and possible effects of instantaneous temperatures on yield components at different CO2 concentrations are required. Nevertheless, the results obtained suggest that the benefits to winter wheat grain yield from CO2 doubling are offset by an increase in mean seasonal temperature of only 1·0 °C to 1·8 °C in the UK.
Developmental and tillering responses of winter wheat (Triticum aestivuni) crops to CO2 and temperature
- G. R. Batts, T. R. Wheeler, J. I. L. Morison, R. H. Ellis, P. Hadley
-
- Journal:
- The Journal of Agricultural Science / Volume 127 / Issue 1 / August 1996
- Published online by Cambridge University Press:
- 27 March 2009, pp. 23-35
-
- Article
- Export citation
-
Winter wheat (Triticum aestivum L., cv. Hereward) was grown in the field within four double-walled polyethylene-covered tunnels along which near-linear temperature gradients were imposed at normal atmospheric or at an elevated CO2 concentration (c. 700 μmol mol−1 CO2) in 1991/92 and in a further experiment in 1992/93. Development was more rapid the warmer the temperature. In 1991/92 an increase in mean seasonal temperature of 3·5 °C reduced the duration from sowing to harvest maturity (the stage when grain moisture content reduced naturally to 15–18%) by c. 38 days, and reduced the duration from the double ridge stage to harvest maturity by c. 34 days. A similar difference resulted from only 1·6 °C warming in 1992/93. Although the range of mean seasonal temperatures differed between years, the relation between temperature and rate of development from sowing to harvest maturity was common to both years (base temperature, −0.8 °C; thermal time 2410 °C d). Carbon dioxide concentration had no effect on this relation or on that between temperature and the rate of development from sowing to the double ridge stage and from the double ridge stage to harvest maturity. Carbon dioxide enrichment increased tillering substantially in 1991/92; there were 200 more shoots m−2 at terminal spikelet formation in crops grown at elevated compared to normal CO2 (additional shoots were principally coleoptile tillers and those developing after tiller 2) and this difference was reduced to 100 shoots m−2 approaching harvest maturity (additional shoots remaining were those developing after tiller 2). In contrast, no effect of CO2 enrichment on tillering was detected at any stage of development in 1992/93. The number of tillers per plant at terminal spikelet formation was a linear function of main stem dry weight at this developmental stage; this relationship was not affected by year or CO2. As CO2 enrichment increased main stem dry weight in the first year only, when main stem dry weights at normal CO2 were only one half of those values determined in the following year, it is concluded that any benefit of increase in CO2 concentration to tillering in winter wheat may be greatest in those crop production environments where main stem dry weights at terminal spikelet are least and vice versa.
Turbulent mixing of passive and chemically reacting species in a low-speed shear layer
- R. G. Batt
-
- Journal:
- Journal of Fluid Mechanics / Volume 82 / Issue 1 / 19 August 1977
- Published online by Cambridge University Press:
- 12 April 2006, pp. 53-95
-
- Article
- Export citation
-
A series of experiments has been conducted in a low-speed wind tunnel in which measurements were performed in a two-dimensional turbulent shear layer experiencing the mixing of both a passive and a chemically reacting species. The low-temperature air in the jet's primary flow was seeded with dilute concentrations of N2O4 so that the dissociation reaction N2 + N2O4 [harr ] 2NO2 + N2 occurred in a near-equilibrium manner within the mixing layer owing to the turbulent mixing properties and the imposed temperature gradient. Mean and fluctuating values of velocity, temperature and NO2 concentration were measured up to axial distances of 25 in. for jet velocities of 23 and 50ft/s (Rex [les ] 7 × 105) and for three primary temperatures (252, 273 and 305°K). Velocity and temperature measurements were performed with hot-wire probes, whereas a fibre optics light sensor probe was used to measure NO2 concentrations. Local correlations between species and other fluid properties were obtained by positioning a hot-wire sensor within the light gap of the fibre optics probe and simultaneously recording output signals from both probes. A relatively complete set of turbulent statistics was measured for the non-reacting shear layer, including such results as temperature/species correlations, probability densities, filtered and unfiltered moving-frame velocities, skewness and flatness factors, spectra, velocity and temperature integral scales, intermittency factors for velocity, temperature and passive species, and conventional intensities. Some typical results from the investigation are as follows: the turbulent Schmidt and Lewis numbers were 0·5 and 1·0 respectively; the correlation between passive NO2 concentration and temperature was approximately 0·95; dramatic changes consistent with equilibrium chemistry occurred in NO2 concentration profiles with chemical reaction; velocity, temperature and concentration spectra were comparable over a 2½-decade range in wavenumber (k−2); spectra, probability densities, time-trace data and smoke-seeded shear-layer photographs indicate that, for axial locations x = x0 [ges ] 18·5 in. and for speeds u1 [ges ] 23ft/s, undisturbed edge fluid rarely penetrates completely across the mixing region. Although not specifically addressed during the current study, measured results herein suggest that the turbulent motion for the present shear layer is characterized more by random and/or three-dimensionality effects than by large-scale two-dimensional coherent structures, as has been observed recently in other shear-layer investigations.
Boundary layer entrainment of sand-sized particles at high speed
- R. G. BATT, M. P. PETACH, S. A. PEABODY, R. R. BATT
-
- Journal:
- Journal of Fluid Mechanics / Volume 392 / 10 August 1999
- Published online by Cambridge University Press:
- 10 August 1999, pp. 335-360
-
- Article
- Export citation
-
An experimental study of entrainment of sand-sized particles in turbulent boundary layers has been performed in a high-speed wind tunnel at square-pulse flow speeds of 27 to 101 ms−1 and for soil bed lengths varying from 2.1 to 5.8 m. Because of high particle drag-to-weight ratios (D/W = 100–1000) and friction velocities (uf) well above soil threshold friction velocities (uft; 10 [les ] uf/uft [les ] 40), the present results correspond to the suspension regime of dust lofting, in contrast to low-speed saltation flows (1 [les ] uf/uft [les ] 5; D/W / 15). Results are obtained characterizing particle entrainment for both a natural soil (White Sands Missile Range (WSMR) sand; 50% finer-by-weight diameter,
D 50 = 180 μm) and a monosized sand sample (Ottawa sand,D 50 = 250 μm). Measurements of local boundary layer velocities and dust densities were performed with traversing state-of-the-art diagnostics. Scouring rate data (0.015 [les ]m s [les ] 0.30 g cm−2 s−1) and streamwise soil flux (10 [les ] Q [les ] 150 g cm−1 s−1) as a function of bed length and velocity were determined.Scouring rates were found to increase as the 3/2-power of velocity, but decay as the inverse square root of dust bed length. Corresponding streamwise soil fluxes (also known as soil loss rates) increased to the 3/2-power of velocity in contrast to the cube power dependence for low-speed results (ufree-stream [les ] 15 m s−1; Q [les ] 1.5 g cm−1 s−1). Comparison of scouring rate data (from pre/post-test soil loss measurements) with derived data based on the rate of change of streamwise flux with distance was favourable. WSMR rates were always lower than Ottawa sand rates, a result consistent with the lower repose angle for the Ottawa sand sample.
Both sets of soil data demonstrate that dust edges extend vertically to higher elevations than corresponding velocity edges. This result implies that the turbulent Schmidt number for the present flows is less than unity and of the order of 0.7. Favourable collapsing of the scouring rate data base was achieved when measured rates were normalized by the friction velocity mass flux, square root of edge Mach number and sand repose angle ratio. A universal rate of 0.3±0.1 correlated well with the bulk of the data.
Yield and partitioning in crops of contrasting cultivars of winter wheat in response to CO2 and temperature in field studies using temperature gradient tunnels
- G. R. BATTS, R. H. ELLIS, J. I. L. MORISON, P. N. NKEMKA, P. J. GREGORY, P. HADLEY
-
- Journal:
- The Journal of Agricultural Science / Volume 130 / Issue 1 / February 1998
- Published online by Cambridge University Press:
- 01 February 1998, pp. 17-27
-
- Article
- Export citation
-
Diverse cultivars of winter wheat (Triticum aestivum L.) were grown in the field in 1993/94 and 1994/95 at Reading UK in temperature gradient tunnels at normal atmospheric (c. 370) or elevated CO2 concentration (c. 700 μmol CO2 mol−1 air). In 1993/94, grain yield of cv. Avalon was insensitive to mean temperature (between 8·8 and 10·9°C), while elevated CO2 increased yield by 1·3 t ha−1 (12·6%). In all other cultivars, warming reduced grain yield and CO2 increased grain yield. In 1993/94, in cvs Galahad and Mercia the effects of CO2 and temperature on yield were additive. However, for cv. Hereward in both years and for cv. Soissons in 1994/95, there were negative interactions between the effects of CO2 and temperature on yield: the maximum benefit of doubling CO2 to grain yield, 4·5 and 2·7 t ha−1 (65 and 29%) respectively, occurred at cooler temperatures; there was no benefit from doubling CO2 (i.e. 0%) once the temperature had increased above the seasonal mean by 2·2–2·6°C in cv. Hereward and by 1·3°C in cv. Soissons. The beneficial effect of doubling CO2 on grain yield in cvs Galahad, Hereward, Mercia and Soissons was negated by an increase in mean seasonal temperature of only 0·7–2·0°C. Warming decreased root dry mass at anthesis in 1994/95 while it increased at elevated CO2 (49 and 186%, coolest and warmest regime, respectively). Carbon partitioned to roots declined progressively with warming, while at elevated CO2 there was an average of 56% increase in allocation to roots. The relative impacts of both CO2 and temperature were greater on root dry mass than on either grain yield or total above-ground biomass, while the effects on grain and biomass yield varied considerably between cultivars, suggesting that the impact of rising CO2 and temperature are likely to be dependent on cultivar.