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Introduction: Patients undergoing emergency abdominal surgery for inflammatory bowel disease (IBD) are a complex cohort who are relatively poorly represented in published literature. This is partly due to the lack of consensus of the definition of the term emergency in IBD surgery. There is ongoing and recent work defining clinical urgency for unplanned surgical procedures and categorizing the high‐risk surgical patient. This paper aims to report the difference in patient metrics and risks as recorded by the National Emergency Laparotomy Audit (NELA). Methods: Complete patient data, including histology, were available in the NELA database between 2013 and 2016. Urgency categories recorded by NELA are <2 h, 2–6 h, 6–18 h, and >18 h. Patient characteristics, physiology, biochemistry, and outcomes are reported according to these urgency categories with regression analysis used to compare differences between them. Results: Mortality in Crohn's disease (CD) ranged from 1.4% in the >18 h urgency to 14.6% in the most urgent. In ulcerative colitis (UC), this range was from 3.1% to 14.8%. In both CD and UC, there were significant trends in hemodynamic instability, serum white cell count, serum electrolytes and creatinine, and outcome measures length of stay and unplanned return to theater. Conclusions: Patients having emergency surgery for IBD are not a single cohort when considering physiology, blood biochemistry, or most importantly, outcomes. Risk counseling and management should reflect this. Hemodynamic changes are subtle and may be missed in this cohort. [ABSTRACT FROM AUTHOR]

In this study, Zea mays L. was grown in indoor controlled environment chambers with a uniform daytime temperature of 30°C, and night-time temperatures of 30, 25, 20, or 15°C. Responses of net photosynthesis (PN) of mature leaves at high PPFD to intercellular CO2 concentrations (Ci) were measured at 20, 25, and 30°C using a new method that generates a complete PN vs. Ci curve in less than four minutes. Results indicated that photosynthesis measured at both Ci values of 25 and 150 µmol mol-1 increased strongly with measurement temperature in plants grown with night temperatures of 25 and 30°C, but there was a much smaller change in photosynthesis with temperature in plants grown with night temperatures of 15 or 20°C. These results indicate that the acclimation of photosynthesis to temperature in this C4 species is substantially affected by night temperature. [ABSTRACT FROM AUTHOR]

Aim: The medical management of inflammatory bowel disease (IBD) is rapidly progressing; however, many patients with the disease still require surgery. Often this is done as an emergency. Initiatives such as the National Emergency Laparotomy Audit have shown how evidence‐based emergency surgery improves outcomes for the patient. The aim of this scoping review is to describe the current evidence base on risk stratification in emergency abdominal surgery for IBD. Methods: A literature search, abstract and full paper screening resulted in 17 articles representing 63 472 patients from seven countries. Results: It is likely that age, the American Society of Anesthesiologists grade, comorbidity and organ dysfunction play a similar role in risk stratification in IBD patients as in other emergency abdominal surgery cohorts. However, the reporting of what is considered an IBD emergency is variable. Six studies include clear definitions of emergency in our study. The range of what is considered an emergency is within 12 h of admission to any time within an unplanned admission. Conclusion: To have data driven, evidence‐based emergency surgical practice in IBD we need consistency of reporting, including the definitions of emergency and urgency. Core descriptor sets in IBD would be valuable. [ABSTRACT FROM AUTHOR]

Introduction: Emergency laparotomy may be required in patients with inflammatory bowel disease (IBD). NELA is the largest prospectively maintained database of adult emergency laparotomies in England and Wales and includes clinical urgency of the cases. The impact of surgeon subspeciality on outcomes after emergency laparotomy for IBD is unclear. We have investigated this association, according to the degree of urgency in IBD emergency laparotomy, including the effect of minimally invasive surgery (MIS). Methods: Adults with IBD in the NELA database between 2013 and 2016 were included. Surgeon subspeciality was colorectal or non-colorectal. Urgencies are 'Immediate', '2–6 h', '6–18 h' and '18–24 h'. Logistic regression was used to investigate in-patient mortality and post-operative length of stay (LOS). Results: There was significantly reduced mortality and LOS in IBD patients who were operated on by a colorectal surgeon in the least urgent category of emergency laparotomies; Mortality adjusted OR 2.99 (CI 1.2–7.8) P = 0.025, LOS IRR 1.18 (CI 1.02–1.4) P = 0.025. This association was not seen in more urgent categories. Colorectal surgeons were more likely to use MIS, P < 0.001, and MIS was associated with decreased LOS in the least urgent cohort, P < 0.001, but not in the other urgencies. Conclusions: We found improved outcomes in the least urgent cohort of IBD emergency laparotomies when operated on by a colorectal surgeon in comparison to a non-colorectal general surgeon. In the most urgent cases, there was no benefit in the operation being performed by a colorectal surgeon. Further work on characterising IBD emergencies by urgency would be of value. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic has resulted in over 340 million infection cases (as of 21 January 2022) and more than 5.57 million deaths globally. In reaction, science, technology and innovation communities across the globe have organised themselves to contribute to national responses to COVID-19 disease. A significant contribution has been from the establishment of wastewater-based epidemiological (WBE) surveillance interventions and programmes for monitoring the spread of COVID-19 in at least 55 countries. Here, we examine and share experiences and lessons learnt in establishing such surveillance programmes. We use case studies to highlight testing methods and logistics considerations associated in scaling the implementing of such programmes in South Africa, the Netherlands, Turkey and England. The four countries were selected to represent different regions of the world and the perspective based on the considerable progress made in establishing and implementing their national WBE programmes. The selected countries also represent different climatic zones, economies, and development stages, which influence the implementation of national programmes of this nature and magnitude. In addition, the four countries’ programmes offer good experiences and lessons learnt since they are systematic, and cover extensive areas, disseminate knowledge locally and internationally and partnered with authorities (government). The programmes also strengthened working relations and partnerships between and among local and global organisations. This paper shares these experiences and lessons to encourage others in the water and public health sectors on the benefits and value of WBE in tackling SARS-CoV-2 and related future circumstances. [ABSTRACT FROM AUTHOR]

Background: Guidelines for urgent investigation of colorectal cancer (CRC) are based on age and symptom-based criteria. This study aims to compare the diagnostic value of clinical features and faecal immunochemical test (FIT) results to identify those at a higher risk of CRC, thereby facilitating effective triage of patients. Methods: We undertook a review of all patients referred for investigation of CRC at our centre between September 2016 and June 2018. Patients were identified using a prospectively recorded local database. We performed a logistic regression analysis of factors associated with a diagnosis of CRC. Results: One-thousand-and-seven-hundred-eighty-four patients with FIT results were included in the study. Change in bowel habit (CIBH) was the most common referring clinical feature (38.3%). Patients diagnosed with CRC were significantly older than those without malignancy (74.0 years vs 68.9 years, p = 0.0007). Male patients were more likely to be diagnosed with CRC than females (6.5% vs 2.5%, Chi-squared 16.93, p < 0.0001). CRC was diagnosed in 3.5% (24/684) with CIBH compared to 8.1% (6/74) with both CIBH and iron deficiency anaemia. No individual or combination of referring clinical features was associated with an increased diagnosis of CRC (Chi-squared, 8.03, p = 0.155). Three patients with negative FIT results (< 4 µg Hb/g faeces) were diagnosed with CRC (3/1027, 0.3%). The highest proportion of cancers detected was in the ≥ 100 µg Hb/g faeces group (55/181, 30.4%). Conclusion: In a multivariate model, FIT outperforms age, sex and all symptoms prompting referral. FIT has greater stratification value than any referral symptoms. FIT does have value in patients with iron deficiency anaemia. [ABSTRACT FROM AUTHOR]

Purpose: Primary care studies suggest that thrombocytosis (platelet counts > 400 × 109/L) is associated with an increased risk of colorectal cancer (CRC). We aimed to establish whether this marker has significant stratification value in patients seen in secondary care. Methods: A retrospective review of 2991 patients referred to our colorectal 2-week-wait (2WW) pathway between August 2014 and August 2017. Patient demographics were recorded prospectively, and local electronic records systems were used to retrieve full blood counts (FBC) and cancer diagnoses. Patients with no recent platelet count at the time of referral or incomplete records were excluded. Results: 2236 patients were included in this evaluation. There was no significant difference in the age distribution of those with thrombocytosis and those without. There were significantly more females in the thrombocytosis group (72.1% vs 53.9%, chi-squared 24.63, p < 0.0001). 130 CRCs were detected (5.8%) and patients with thrombocytosis were more likely to have CRC (OR 2.62, 95% CI 1.60–4.30). The CRC diagnosis rate was significantly higher in females with thrombocytosis (10.3% vs 2.9%, chi-squared 19.41, p < 0.0001) and males with thrombocytosis (16.1% vs 7.9%, chi-squared 4.62, p = 0.032). Conclusion: Thrombocytosis appears to have stratification value in the 2WW population. Further evaluation of its value alone or in combination with other stratification tests is required. [ABSTRACT FROM AUTHOR]

Background: New national guidance on urgent referral for investigation of colorectal cancer included faecal occult blood testing in 2015. A service evaluation of faecal immunochemical testing (FIT) and anaemia as risk stratification tools in symptomatic patients suspected of having CRC was undertaken. Methods: Postal FIT was incorporated into the colorectal cancer 2‐week wait (2WW) pathway for all patients without rectal bleeding in 2016. Patients were investigated in the 2WW pathway as normal, and outcomes of investigations were recorded prospectively. Anaemia was defined as a haemoglobin level below 120 g/l in women and 130 g/l in men. Results: FIT kits were sent to 1106 patients, with an 80·9 per cent return rate; 810 patients completed investigations and 40 colorectal cancers were diagnosed (4·9 per cent). FIT results were significantly higher in patients with anaemia (median (i.q.r.) 4·8 (0·8–34·1) versus 1·2 (0–6·4) μg Hb/g faeces in those without anaemia; P < 0·001). Some 60·4 per cent of patients (538 of 891) had a result lower than 4 μg haemoglobin (Hb) per g faeces (limit of detectability), and 69·7 per cent (621 of 891) had less than 10 μg Hb/g faeces. Some 60 per cent of patients with colorectal cancer had a FIT reading of 150 μg Hb/g faeces or more. For five colorectal cancers diagnosed in patients with a FIT value below 10 μg Hb/g faeces, there was either a palpable rectal mass or the patient was anaemic. A FIT result of more than 4 μg Hb/g faeces had 97·5 per cent sensitivity and 64·5 per cent specificity for a diagnosis of colorectal cancer. A FIT result above 4 μg Hb/g faeces and/or anaemia had a 100 per cent sensitivity and 45·3 per cent specificity for colorectal cancer diagnosis. Conclusion: FIT is most useful at the extremes of detectability; strongly positive readings predict high rates of colorectal cancer and other significant pathology, whereas very low readings in the absence of anaemia or a palpable rectal mass identify a group with very low risk. High return rates for FIT within this 2WW pathway indicate its acceptability. [ABSTRACT FROM AUTHOR]

C photosynthesis at high light is often modeled by assuming limitation by the maximum capacity of Rubisco carboxylation (V) at low CO concentrations, by electron transport capacity (J) at higher CO concentrations, and sometimes by triose-phosphate utilization rate at the highest CO concentrations. Net photosynthetic rate ( P ) at lower light is often modeled simply by assuming that it becomes limited by electron transport (J). However, it is known that Rubisco can become deactivated at less than saturating light, and it is possible that P at low light could be limited by the rate of Rubisco carboxylation ( V ) rather than J. This could have important consequences for responses of P to CO and temperature at low light. In this work, P responses to CO concentration of common bean, quinoa, and soybean leaves measured over a wide range of temperatures and PPFDs were compared with rates modeled assuming either VC or J limitation at limiting light. In all cases, observed rates of P were better predicted by assuming limitation by VC rather than J at limiting light both below and above the current ambient CO. One manifestation of this plant response was that the relative stimulation of P with increasing the ambient CO concentration from 380 to 570 µmol mol did not decrease at less than saturating PPFDs. The ratio of VC to V at each lower PPFD varied linearly with the ratio of P at low PPFD to P at high PPFD measured at 380 µmol(CO) mol in all cases. This modification of the standard C biochemical model was much better at reproducing observed responses of light-limited P to CO concentrations from pre-industrial to projected future atmospheric concentrations. [ABSTRACT FROM AUTHOR]

Responses to drought were studied using two maize inbred lines (B76 and B106) and a commercial maize hybrid ( Zea mays L. cv. Silver Queen) with differing resistance to abiotic stress. Maize seedlings were grown in pots in controlled environment chambers for 17 days and watering was withheld from one half the plants for an additional 11 days. On the final treatment date, leaf water potentials did not differ among genotypes and were −0.84 and −1.49 MPa in the water sufficient and insufficient treatments, respectively. Greater rates of CO assimilation were retained by the stress tolerant maize inbred line, B76, in comparison to the other two genotypes 11 days after watering was withheld. Rates of CO assimilation for all three genotypes were unaffected by decreasing the measurement O concentration from 21 to 2% (v/v). Activities of phospho enolpyruvate carboxylase (PEPC), NADP-malic enzyme (NADP-ME), and NADP malate dehydrogenase were inhibited from 25 to 49% by the water deficiency treatment. Genotypic differences also were detected for the activities of NADP-ME and for PEPC. Changes of transcript abundance for the three C pathway enzymes also varied among watering treatments and genotypes. However, examples where transcripts decreased due to drought were associated with the two stress susceptible genotypes. The above results showed that enzymes in the C photosynthetic pathway were less inhibited by drought in stress tolerant compared to stress susceptible maize genotypes. [ABSTRACT FROM AUTHOR]

We hypothesized that decreased stomatal conductance ( g) at elevated CO might decrease transpiration ( E), increase leaf water potential (Ψ), and thereby protect net photosynthesis rate ( P) from heat damage in maize ( Zea mays L) seedlings. To separate long-term effects of elevated CO, plants grew at either ambient CO or elevated CO. During high-temperature treatment (HT) at 45°C for 15 min, leaves were exposed either to ambient CO (380 μmol mol) or to elevated CO (560 μmol mol). HT reduced P by 25 to 38% across four CO combinations. However, the g and E did not differ among all CO treatments during HT. After returning the leaf temperature to 35°C within 30 min, g and E were the same or higher than the initial values. Leaf water potential (Ψ) was slightly lower at ambient CO, but not at elevated CO. This study highlighted that elevated CO failed in protecting P from 45°C via decreasing g and Ψ. [ABSTRACT FROM AUTHOR]

The carbon dioxide concentration in free air carbon dioxide enrichment (FACE) systems typically has rapid fluctuations. In our FACE system, power spectral analysis of CO concentration measured every second with an open path analyzer indicated peaks in variation with a period of about one minute. I used open-top chambers to expose cotton and wheat plants to either a constant elevated CO concentration of 180 μmol mol above that of outside ambient air, or to the same mean CO concentration, but with the CO enrichment cycling between about 30 and 330 μmol mol above the concentration of outside ambient air, with a period of one minute. Three short-term replicate plantings of cotton were grown in Beltsville, Maryland with these CO concentration treatments imposed for 27-day periods over two summers, and one winter wheat crop was grown from sowing to maturity. In cotton, leaf gas-exchange measurements of the continuously elevated treatment and the fluctuating treatment indicated that the fluctuating CO concentration treatment consistently resulted in substantial down-regulation of net photosynthetic rate ( P) and stomatal conductance ( g). Total shoot biomass of the vegetative cotton plants in the fluctuating CO concentration treatment averaged 30% less than in the constantly elevated CO concentration treatment at 27 days after planting. In winter wheat, leaf gas-exchange measurements also indicated that down-regulation of P and g occurred in flag leaves in the fluctuating CO concentration treatment, but the effect was not as consistent in other leaves, nor as severe as found in cotton. However, wheat grain yields were 12% less in the fluctuating CO concentration treatment compared with the constant elevated CO concentration treatment. Comparison with wheat yields in chambers without CO addition indicated a nonsignificant increase of 5% for the fluctuating elevated CO concentration treatment, and a significant increase of 19% for the constant elevated treatment. The results suggest that treatments with fluctuating elevated CO concentrations could underestimate plant growth at projected future atmospheric CO concentrations. [ABSTRACT FROM AUTHOR]

Some reports indicate that mesophyll conductance ( g) to carbon dioxide varies greatly with the substomatal carbon dioxide concentration ( C) during the measurement, while other reports indicate little or no change in g with C. I used the oxygen sensitivity of photosynthesis to determine the response of g to C over the range of about 100 to 300 μmol mol C at constant temperature in common bean ( Phaseolus vulgaris) and soybean ( Glycine max) grown over a range of temperatures and photosynthetic photon flux densities (PPFD). In soybean grown and measured at high PPFD there was only a slight, approximately 15% decrease in g with C over the range of 100 to 300 μmol mol. With lower PPFD during the measurement of g, and especially with low PPFD during plant growth, there was a larger decrease in g with C in soybean. In common bean, the same range in C resulted in about a 60% decrease in g for plants grown and measured at high PPFD, with an even larger decrease for plants at low growth or measurement PPFD. Growth temperatures of 20 to 30°C had little influence on the response of g to C or its absolute value in either species. It is concluded that these two species differed substantially in the sensitivity of g to C, and that PPFD but not temperature during leaf development strongly affected the response of g to C. [ABSTRACT FROM AUTHOR]

To examine the impact of projected climate changes on secondary succession, we exposed the same fallow soil with a common seed bank to an in situ gradient of urban to rural macroenvironments that differed in temperature and CO2 concentration ([CO2]). This gradient was established at three locations: Baltimore city center (urban), a city park on the outskirts of Baltimore (suburban), and an organic farm 87 km from the Baltimore city center site (rural). Over a five-year period, the urban site averaged 2.1°C warmer and had a [CO2] that was ~20% higher than at the rural location, indicating that this gradient was a reasonable surrogate for projected changes in those variables for this century. Previous work had demonstrated that other abiotic variables measured across the transect, including tropospheric ozone and nitrogen deposition, did not differ consistently. The first year of exposure resulted in (two- to threefold) greater aboveground biomass in the urban relative to the rural site, but with uniform species composition across sites. Simple regression of abiotic variables indicated that temperature and vapor pressure deficit (VPD) were the best predictors of plant biomass among locations. Stepwise multiple regressions were also performed to analyze the effect of more than one macroenvironmental variable on total plant biomass. The combination of daily CO2 concentration and nighttime temperature explained 87% ( P < 0.01) of the variability in total biomass between sites. After five years, the species demography of the plant communities had changed significantly, with a greater ratio of perennials to annuals for the urban relative to the rural location. Greater first-year biomass and litter accumulation at the urban site may have suppressed the subsequent seed germination of annual species, accelerating changes in species composition. If urban macroenvironments reflect future global change conditions, these data suggest a faster rate of secondary succession in a warmer, higher [CO2] world. [ABSTRACT FROM AUTHOR]

The carbon dioxide concentrating system in C4 photosynthesis allows high net photosynthetic rates ( PN) at low internal carbon dioxide concentrations ( Ci), permitting higher PN relative to stomatal conductance ( gs) than in C3 plants. This relation would be reflected in the ratio of Ci to external ambient ( Ca) carbon dioxide concentration, which is often given as 0.3 or 0.4 for C4 plants. For a Ca of 360 µmol mol−1 that would mean a Ci about 110–140 µmol mol−1. Our field observations made near midday on three weedy C4 species, Amaranthus retroflexus, Echinochloa crus-galli, and Setaria faberi, and the C4 crop Sorghum bicolor indicated mean values of Ci of 183–212 µ mol mol−1 at Ca = 360 µmol mol−1. Measurements in two other C4 crop species grown with three levels of N fertilizer indicated that while midday values of Ci at high photon flux were higher at limiting N, even at high nitrogen Ci averaged 212 and 196 µmol mol−1 for Amaranthus hypochondriacus and Zea mays, respectively. In these two crops midday Ci decreased with increasing leaf to air water vapor pressure difference. Averaged over all measurement days, the mean Ci across all C4 species was 198 µmol mol−1, for a Ci/ Ca ratio of 0.55. Prior measurements on four herbaceous C3 species using the same instrument indicated an average Ci/ Ca ratio of 0.69. Hence midday Ci values in C4 species under field conditions may often be considerably higher and more similar to those of C3 species than expected from measurements made on plants in controlled environments. Reducing gs in C4 crops at low water vapor pressure differences could potentially improve their water use efficiency without decreasing PN. [ABSTRACT FROM AUTHOR]

Some studies of responses of plants to elevated concentrations of carbon dioxide (EC) added CO2 only in the daytime, while others supplied CO2 continuously. I tested whether these two methods of EC treatments produced differences in the seed yield of soybeans. Tests were conducted for four growing seasons, using open top chambers, with soybeans rooted in the ground in field plots. One third of the chambers were flushed with air at the current ambient [CO2] (AC), one third had [CO2] 350 µmol mol−1 above ambient during the daytime (ECd), while one third had [CO2] 350 µmol mol−1 above ambient for 24 h per day (ECdn). ECdn increased seed yield by an average of 62 % over the four years compared with the AC treatment, while ECd increased seed yield by 34 %. Higher seed yield for ECdn compared with ECd occurred each year. In comparing years, the relative yield disadvantage of ECd decreased with increasing overall seed yield. On days with high water vapor pressure deficits, soybean canopies with ECd had smaller midday extinction coefficients for photosynthetically active radiation than canopies with ECdn, because of a more vertical leaf orientation. Hence the seed yield of soybean at EC varied depending on whether EC was also provided at night, with much greater yield stimulation for ECdn than for ECd in some years. [ABSTRACT FROM AUTHOR]

To examine the impact of climate change on vegetative productivity, we exposed fallow agricultural soil to an in situ temperature and CO2 gradient between urban, suburban and rural areas in 2002. Along the gradient, average daytime CO2 concentration increased by 21% and maximum (daytime) and minimum (nighttime) daily temperatures increased by 1.6 and 3.3°C, respectively in an urban relative to a rural location. Consistent location differences in soil temperature were also ascertained. No other consistent differences in meteorological variables (e.g. wind speed, humidity, PAR, tropospheric ozone) as a function of urbanization were documented. The urban-induced environmental changes that were observed were consistent with most short-term (~50 year) global change scenarios regarding CO2 concentration and air temperature. Productivity, determined as final above-ground biomass, and maximum plant height were positively affected by daytime and soil temperatures as well as enhanced [CO2], increasing 60 and 115% for the suburban and urban sites, respectively, relative to the rural site. While long-term data are needed, these initial results suggest that urban environments may act as a reasonable surrogate for investigating future climatic change in vegetative communities. [ABSTRACT FROM AUTHOR]

Leaf area expansion, photosynthetic carbon dioxide uptake and leaf dry mass accumulation were compared for expanding leaves of well-watered soybean (Glycine max [L.] Merr.) plants, mildly dehydrated plants and well-watered plants treated with abscisic acid (ABA). Both ABA treatment and dehydration reduced area expansion in the light and over a 24 h period without decreasing the photosynthetic rates of expanding leaves. Dry mass accumulation during the light was less in ABA-treated and water-stressed leaves than in control leaves, with no differences among treatments in leaf mass per unit of area. ABA treatment and water stress both increased export of carbon from expanding leaves in the light. ABA applied near the end of the light period also increased export of carbon during the following dark period. However, it is unlikely that decreased availability of photosynthate caused slow expansion in the ABA and dehydration treatments, because expansion rates were not slowed in plants kept in dim light, even though photosynthetic rates and dry mass accumulation rates were greatly reduced. The data suggest that ABA may mediate the effects of mild dehydration on leaf area expansion and partitioning of photosynthate. [ABSTRACT FROM AUTHOR]

Gas exchange measurements were made on single leaves of three C3 and one C4 species at air speeds of 0.4 and 4.0 m s-1 to determine if boundary layer conductance substantially affected the sub- stomatal pressure of carbon dioxide. Boundary layer conductances to water vapour were 0.4 to 0.5 mol m-2 s-1 at the lower air speed, and 1.2 to 1.5 mol m-2 s-1 at the higher air speed. Substonmatal carbon dioxide pressures were about 5 Pa lower at low boundary layer conductance in the C3 species, and about 3 Pa lower in the C4 species when measurements were made at high and moderate photosynthetic photon flux densities. No evidence of stomatal adjustment to altered boundary layer conductance was found. Photosynthetic rates at high photon flux densities were reduced by about 20% at the low air speed in the C3 species. The commonly reported values of substomatal carbon dioxide pressure for C3 and C3 species were found to occur only when measurements were made at the higher air speed. [ABSTRACT FROM AUTHOR]

Soybeans were grown at three CO2 concentrations in outdoor growth chambers and at two concentrations in controlled-environment growth chambers to investigate the interactive effects of CO2, temperature and leaf-to-air vapour pressure difference (LAVPD) on stomatal conductance. The decline in stomatal conductance with CO2 was a function of both leaf temperature and LAVPD. In the field measurements, stomatal conductance was more sensitive to LAVPD atlow CO2 at 30 °C but not at 35 °C. There was also a direct increase in conductance with temperature, which was greater at the two elevated carbon dioxide concentrations. Environmental growthchamber results showed that the relative stomatal sensitivity to LAVPD decreased with both leaf temperature and CO2. Measurements in the environmental growth chamber were also performed at the opposing CO2, and these experiments indicate that the stomatal sensitivity to LAVPD was determined more by growth CO2 than by measurement CO2. Two models that describe stomatal responses to LAVPD were compared with the outdoor data to evaluate whether these models described adequately the interactive effects of CO2, LAVPD and temperature. [ABSTRACT FROM AUTHOR]

Three types of observations were used to test the hypothesis that the response of stomatal conductance to a change in vapour pressure deficit is controlled by whole-leaf transpiration rate or by feedback from leaf water potential. Varying the leaf water potential of a measured leaf by controlling the transpiration rate of other leaves on the plant did not affect the response of stomatal conductance to vapour pressure deficit in Glycine max. In three species, stomatal sensitivity to vapour pressure deficit was eliminated when measurements were made at near-zero carbon dioxide concentrations, despite the much higher transpiration rates of leaves at low carbon dioxide. In Abutilon theophrasti, increasing vapour pressure deficit sometimes resulted in both decreased stomatal conductance and a lower transpiration rate even though the response of assimilation rate to the calculated substomatal carbon dioxide concentration indicated that there was no 'patchy' stomatal closure at high vapour pressure deficit in this case. These results are not consistent with stomatal closure at high vapour pressure deficit caused by increased whole-leaf transpiration rate or by lower leaf water potential. The lack of response of conductance to vapour pressure deficit in carbon dioxide-free air suggests that abscisic acid may mediate the response. [ABSTRACT FROM AUTHOR]

Soybean plants were grown continuously at 350 and 700 cm3 m-3 CO2 at constant temperature. Respiration rates of third trifoliolate leaves were measured at the growth CO2 concentration for the whole dark period from 5 d before through to 5 d after full area expansion. The short-term response of respiration rate to the measurement CO2 concentration was also determined at each age. Respiration rates per unit of dry mass declined with age and were significantly less at a given age or RGR in leaves grown and measured at the elevated CO2. The difference in respiration rate was largest in mature leaves and resulted from the different measurement CO2 concentrations. The respiratory costs of the tissue synthesis, estimated from the elemental composition of the tissue, did not differ substantially between CO2 treatments. The response of respiration rate to carbon dioxide concentration was not strongly affected by the form of nitrogen supplied. Maintenance respiration calculated by subtracting growth respiration from total respiration was negative in rapidly growing leaves for both CO2 treatments. This Indicates that CO2 efflux in the dark does not accurately reflect the average 24 h rate of energy expenditure on growth and maintenance for soybean leaves. [ABSTRACT FROM AUTHOR]

Experiments were performed to determine if growth at elevated partial pressure of CO2 altered the sensitivity of leaf water vapour conductance and rate of CO2 assimilation to the leaf-to-air difference in the partial pressure of water vapour (Δw). Comparisons were made between plants grown and measured at 350 and 700 μPa Pa-1 partial pressures of CO2 for amaranth, soybean and sunflower grown in controlled environment chambers, soybean grown outdoors in pots, and orchard grass grown in field plots. In amaranth, soybean and orchard grass, both the absolute and the relative sensitivity of conductance to Δw at the leaf surface were less in plants grown and measured at the elevated CO2. In sunflower, there was no change in the sensitivity of conductance to Δw for the two CO2 partial pressures. Tests in soybeans and amaranth showed that the change in sensitivity resulted from elevated CO2 during the measurement of the Δw response. Assimilation rate of CO2 was not altered by Δw in amaranth, which has C4 metabolism. In sunflower, the assimilation rate of plants grown and measured at elevated CO2 was insensitive to Δw, consistent with the response of assimilation rate to intercellular CO2 partial pressure in the prevailing range. In soybean, the sensitivity of assimilation rate to Δw was not different between CO2 treatments, in contrast to what would be expected from the response of assimilation rate to intercellular CO2 partial pressure. [ABSTRACT FROM AUTHOR]

Responses to humidity of net photosynthesis and leaf conductance of single attached leaves were examined in populations of herbs from wet soil sites in Beltsville, Maryland and Davis, California, USA. Plants were grown in controlled environments under three conditions which differed in the magnitude of the day-night temperature difference and in daytime air saturation deficit. No population differences in response were found in Abutilon theophrasti. In Amaranthus hybridus stomatal conductance and net photosynthesis were more reduced by increasing leaf to air water vapor pressure difference (VPD) in the population from Beltsville, but only for the growth condition with a constant 25°C temperature. In Chenopodium album, stomatal conductance was more sensitive to VPD in the population from Davis, but only for the growth condition with 28/22°C day/night temperatures. Population differences in the sensitivity to VPD of leaf conductance were associated with differences in leaf area to root weight ratio. The relative reduction of net photosynthesis as VPD increased was greater than, equal to, or less than the relative decrease in substomatal carbon dioxide partial pressure. The pattern depended on species, and on growth condition. From these results one can not conclude that environmental humidity has been a strong selective force in determining sensitivity to humidity of stomatal conductance. [ABSTRACT FROM AUTHOR]

A new variational characterization of the solution of a matrix Riccati equation is presented. The characterization is given as the maximum Hermitian matrix that makes a certain compound matrix Hermitian positive semidefinite. The shorted operator (Schur complement) applied to the compound matrix produces the Riccati equation. [ABSTRACT FROM AUTHOR]

A transport system has been proposed using buses operating over ordinary roads and over special reserved tracks (busways) on which they might be automatically guided. Using cost and performance data resulting from an earlier technical study (not reported here), a hypothetical network of routes and services in the West Midlands conurbation is studied. Estimates of patronage diverted from public and private transport enable the profitability of the system and its costs and benefits to be assessed. It is concluded that the system could be attractive both in commercial and in cost/benefit terms, providing acceptable means could be found for handling the buses around and through the inner central areas of cities. The net environmental changes, which would result from additional fixed plant permitting more efficient use of mobile plant, have not been quantified. [ABSTRACT FROM PUBLISHER]

Leaf conductance responses to leaf to air water vapour partial pressure difference (VPD) have been measured at air speeds of 0.5 and 3.0 ms-1 in single attached leaves of three species in order to test the hypothesis that leaf conductance response to VPD is controlled by evaporation from the outer surface of the epidermis, rather than by evaporation through stomata. Total conductance decreased linearly with increasing VPD at both air speeds, but was decreased 1.6-3.0 times as much as by a given increase in VPD at high than at low air speed, depending on species. In all species the relationship between leaf conductance and the gradient for evaporation from the epidermis was the same at both values of boundary layer conductance, supporting the hypothesis that direct epidermal evaporation controls stomatal guard cell behaviour in responses of stomata to VPD in these species. [ABSTRACT FROM AUTHOR]

A preview study was conducted to look at localization learning in monaural listeners. Eight subjects with hearing ability within normal limits were selected for the study. The subjects were asked to determine which speaker a signal was coming through with one aided and one plugged ear. The eight subjects were divided into two groups of four, an experimental and a control group. Each subject was tested in three 1 h sittings. Testing was accomplished in an anechoic chamber with eight speakers at 45° intervals. The signal was a narrow band noise, 2400-4800 Hz. Two signal-to-noise ratios were selected, -5 and -10. The noise was white noise. Subjects were allowed to move their heads 180°, 90° to either side. The experimental group received immediate feedback as to the actual speaker the signal was coming through and were allowed to take notes of any clues they could acquire. The control group received no feedback. The results indicated that learning takes place with and without training. However, those subjects who received training exhibited significantly better scores. [ABSTRACT FROM AUTHOR]