CYTOSKELETON, Issue 3 2003
Kazuo Inaba
Abstract Sperm motility in flatfishes shows unique characteristics. The flagellar movement either in vivo or in permeabilized models is arrested by the presence of 25,100 mM HCO3,, or by gentle perfusion with CO2 gas. To understand the molecular basis of this property, sperm Triton-soluble proteins and flagellar proteins from several species were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. An abundant 29-kDa protein was observed only in flatfish species. Partial amino acid sequences identified this protein as a carbonic anhydrase, an enzyme involved in the interconversion of CO2 and HCO3,. 6-ethoxyzolamide, a specific inhibitor of carbonic anhydrase inhibits sperm motility, especially at low pH. In the case of HCO3, -arrested sperm, the motility is restored by addition of 6-ethoxyzolamide. Taken together, these results suggest that a novel pH/ HCO3, -dependent regulatory mechanism mediated by carbonic anhydrase is involved in the motility control in flatfish sperm. Cell Motil. Cytoskeleton 55:174,187, 2003. © 2003 Wiley-Liss, Inc. [source]

Hypothermic insult to the periodontium: a model for the study of aseptic tooth resorption

DENTAL TRAUMATOLOGY, Issue 1 2000
C. W. Dreyer
Abstract , The aim of the current investigation was to define an animal model for the study of hard tissue resorption by examining the responses of the periodontal ligament (PDL) to both single and multiple episodes of hypothermic injury to the crowns of rat teeth. A group of 12 male rats weighing 200,250 g were anesthetized, and pellets of dry ice (CO2) were applied once to the crowns of the right first maxillary molars for continuous periods of 10 or 20 min. Animals were sacrificed at 2, 7, 14 and 28 days and tissues were processed for routine histological examination. A second group of eight animals and a third group of 12 animals were subjected to three applications of dry ice over a period of 1 week and sacrificed at 2 and 14 days respectively after the final application. In addition to thermal insult, the periodontium of teeth from a fourth group of six rats was subjected to mechanical trauma. Examination of the sections from the group undergoing a single freezing episode revealed that, by 1 week, shallow resorption lacunae had appeared on the root surface. These became more extensive after 14 days. At the same time hyaline degeneration was evident in the PDL. Within this group, teeth subjected to the longer 20-min application times generally showed more extensive injuries. By 28 days, evidence of repair was observed with reparative cementum beginning to line the resorption lacunae in the root dentin. Sections from animals subjected to multiple episodes of thermal trauma and those subjected to additional mechanical insult showed more extensive external root resorption than those from single-injury animals. It was concluded that low temperature stimuli applied to the crowns of rat molars were capable of eliciting a sterile degenerative response in the PDL which, in turn, resulted in external root resorption. Furthermore, the degree of this tissue injury was commensurate with the duration and number of exposures to the trauma. The results also indicated that progression of the resorptive process required periodic exposure to the injury, in the absence of which repair to the damaged root occurred. [source]

Behavioral and cardiovascular effects of 7.5% CO2 in human volunteers

DEPRESSION AND ANXIETY, Issue 1 2005
Jayne E. Bailey M.Sc.
Abstract The study of carbon dioxide (CO2) inhalation in psychiatry has a long and varied history, with recent interest in using inhaled CO2 as an experimental tool to explore the neurobiology and treatment of panic disorder. As a consequence, many studies have examined the panic-like response to the gas either using the single or double breath 35% CO2 inhalation or 5,7% CO2 inhaled for 15,20 min, or rebreathing 5% CO2 for a shorter time. However, this lower dose regime produces little physiological or psychological effects in normal volunteers. For this reason we have studied the effects of a higher concentration of CO2, 7.5%, given over 20 min. Twenty healthy volunteers were recruited to a double blind, placebo-controlled study where air and 7.5% CO2 were inhaled for 20 min. Cardiovascular measures and subjective ratings were obtained. When compared to air, inhaling 7.5% CO2 for 20 min increases systolic blood pressure and heart rate, indicating increased autonomic arousal. It also increases ratings of anxiety and fear and other subjective symptoms associated with an anxiety state. The inhalation of 7.5% CO2 for 20 min is safe for use in healthy volunteers and produces robust subjective and objective effects. It seems promising as an anxiety provocation test that could be beneficial in the study of the effects of anxiety on sustained performance, the discovery of novel anxiolytic agents, and the study of brain circuits and mechanisms of anxiety. Depression and Anxiety 00:000,000, 2005. © 2005 Wiley-Liss, Inc. [source]

Effect of Laser Resurfacing on p53 Expression in Photoaged Facial Skin

DERMATOLOGIC SURGERY, Issue 6 2007
MOETAZ M. EL-DOMYATI MD
BACKGROUND p53 overexpression has been reported in photoaged skin. Meanwhile, p53 gene mutations have been implicated as an important factor in the pathogenesis of ultraviolet (UV) light,induced skin cancer. OBJECTIVE The objective was to evaluate the effect of laser resurfacing on the epidermal thickness and expression of p53 in photoaged skin. METHODS Specimens were obtained from the facial skin of 10 patients before and after 3 months and 1 year of treatment using CO2 (five cases) and erbium (Er):YAG (five cases) lasers. Specimens were also obtained from six age-matched controls. These biopsies were used for routine histopathology, histometry, and p53 immunoperoxidase staining. RESULTS Both CO2 and Er:YAG lasers were found to induce a significant decrease in p53 expression in biopsies obtained after 3 months (p=.0004 and .002, respectively) followed by gradual increase (p=.01 in both groups). A significant increase (p<.01) in epidermal thickness was also observed after 1 year of resurfacing. This increase, however, is inversely correlated with the level of p53 expression in such patients. CONCLUSION The decrease in epidermal p53 expression after CO2 and Er:YAG lasers may account for some of the benefits of resurfacing on the epidermis, as well as prevention of actinic neoplasia by adjusting any disturbance in the proliferation/apoptosis balance observed in photoaged facial skin. [source]

Clear Cell Acanthoma Successfully Treated with a Carbon Dioxide Laser

DERMATOLOGIC SURGERY, Issue 10 2005
Ching-Chi Chi MD
Background. The treatment of choice for clear cell acanthoma (CCA) is excision. Resolution after cryotherapy has also been reported but requires three to four courses of treatment. Objective. To demonstrate three CCA lesions in two patients successfully treated with a carbon dioxide (CO2) laser. Methods. Under local anesthesia, these lesions were vaporized by using a CO2 laser in the Silktouch mode with a spot size of 5 mm and a fluence of 20 J/cm2. Two to six passes, as needed, were delivered until the tumor was completely removed. Results. Pain was minimal or nonexistent during and after the operation. No postoperative edema was noted. The wounds healed satisfactorily without scarring. No sign of recurrence was found following operation. Conclusion. The CO2 laser has the advantages of requiring only one course, precise tumor removal, a relatively bloodless surgical field, a short operation time, and less or no postoperative pain and edema. Postoperative wound care is convenient and easy with hydrocolloid and alginate dressings. The patient's quality of life is less adversely affected. The CO2 laser may be appropriate for multiple CCAs, giant CCA, CCA overlying or near joints, CCA refractory to cryotherapy, patients on anticoagulants, and those who cannot tolerate pain from cryotherapy, especially children and the elderly. [source]

Combination Surgical Lifting with Ablative Laser Skin Resurfacing of Facial Skin: A Retrospective Analysis

DERMATOLOGIC SURGERY, Issue 9 2004
Tina S. Alster MD
Background. Cutaneous aging is manifested by rhytides, dyschromias, and skin laxity. Ablative laser skin resurfacing can effectively improve many signs of skin aging; however, the photoaged patient with facial laxity often requires a surgical lifting procedure in order to obtain optimal results. Concerns with delayed or impaired wound healing has led to reluctance to perform both procedures simultaneously. Objective. To report the clinical results and side effect profiles after concomitant surgical facial lifting procedures and ablative carbon dioxide or erbium:YAG laser resurfacing in a series of patients. Methods. A retrospective analysis and chart review was performed in 34 consecutive patients who underwent combination CO2 or erbium:YAG laser skin resurfacing and surgical lifting procedures, including S-lift rhytidectomy, blepharoplasty, and brow lift. Side effects and complication rates were tabulated. Results. The side effect profile of the combined surgical-laser procedures was similar to that reported after a laser-only procedure. The most common side effect was transient hyperpigmentation which occurred in 20.6% of treated patients. None of the patients experienced delayed reepithelialization, skin necrosis, or prolonged healing times. Conclusions. Concurrent laser skin resurfacing and surgical lifting of facial skin maximizes aesthetic results without increased incidence of adverse effects. Patients benefit from the consolidation of anesthesia and convalescent times as well as enhanced global clinical outcomes. [source]

Treatment of Recurrent Ingrown Great Toenail Associated with Granulation Tissue by Partial Nail Avulsion Followed by Matricectomy with Sharpulse Carbon Dioxide Laser

DERMATOLOGIC SURGERY, Issue 5 2002
Kuo-chia Yang MD
background. The effectiveness of partial nail avulsion followed by matricectomy with carbon dioxide (CO2) laser for the treatment of ingrown great toenails remains unclear. objective. This study sought to determine the effectiveness of partial nail avulsion followed by matricectomy with sharpulse CO2 laser in the treatment of recurrent ingrown great toenails associated with granulation tissue. materials and methods. Fourteen patients with a total of 18 recurrent ingrown great toenails were randomly selected for participation in this study. Partial nail avulsions followed by matricectomy with sharpulse CO2 laser were performed on the involved nails. After at least 6 months, we evaluated the recurrence of ingrown toenails, regrowth of the nail spike, duration of post-treatment pain and post-treatment infection. results. Partial nail avulsion followed by matricectomy with sharpulse CO2 laser in the treatment of ingrown toenails resulted in a high cure rate, short postoperative pain duration and low risk of postoperative infection. conclusion. This method we advocate is convenient and effective for the treatment of recurrent ingrown great toenail associated with granulation tissue. [source]

The Effects of Variable Pulse Width of Er:YAG Laser on Facial Skin

DERMATOLOGIC SURGERY, Issue 4 2001
Khalil A. Khatri MD
Background. The use of CO2 and Er:YAG lasers for resurfacing has increased significantly in the past few years. Er:YAG laser causes pinpoint bleeding during and after treatment with a typical pulse width of 250 ,sec. A longer pulse of Er:YAG laser can potentially coagulate dermal blood vessels and increase the residual thermal damage (RTD). Objective. To evaluate the effects of various pulse durations of Er:YAG laser on the depth of RTD and bleeding. Methods. The preauricular skin of a volunteer was exposed to Er:YAG laser at 250-, 350-, and 700-,sec pulse durations, with a fluence of 5 J/cm2. The number of passes varied between 6 and 16. The treated skin was excised and a histologic evaluation was done. Results. The maximum depth of RTD was 50 ,m and there was decreased bleeding with a 700-,sec pulse duration. Conclusion. The increased pulse duration of Er:YAG laser of 700 ,s does not increase the maximum reported RTD and therefore would not change the recovery time and may have a beneficial effect on hemostasis. [source]

Laser-Assisted Hair Transplantation: Histologic Comparison Between CO2 and Ho:YAG Lasers

DERMATOLOGIC SURGERY, Issue 4 2001
Eugene A. Chu MD
Background. Various laser wavelengths and devices have been advocated for use in the creation of recipient channels during hair transplant surgery, including flash-scanned CO2, Ho:YAG (, = 2.12 ,m), and Er:YAG (, = 2.94 ,m). Objective. To determine the tissue injury caused by flash-scanned CO2 and pulsed Ho:YAG lasers during the creation of hair transplant recipient channels and to assess the efficacy of the Ho:YAG laser. Methods. Recipient channels were created in vivo in human scalp tissue using both lasers, and were excised and prepared for histologic examination. Optical micrometry of tissue sections was used to assess thermal injury. Results. The Ho:YAG laser created jagged, irregular-shaped channels with larger zones of thermal injury (superficial deepithelialization, thermal necrosis, and thermal damage). In contrast, the CO2 laser produced well-defined cylindrically shaped channels free of cellular debris with minimal epithelial disruption and significantly less lateral thermal injury. Conclusion. Given that the Ho:YAG produced larger regions of thermal injury and recipient channels that were unacceptable for graft, the CO2 laser remains the better choice for the creation of recipient channels during hair transplant surgery. However, ongoing research will be necessary to determine the optimal laser wavelength and/or devices for this procedure. [source]

Timing and duration of developmental nicotine exposure contribute to attenuation of the tadpole hypercapnic neuroventilatory response

DEVELOPMENTAL NEUROBIOLOGY, Issue 7 2009
Cord M. Brundage
Abstract The ability for air-breathing vertebrates to adjust ventilation in response to increased CO2 (hypercapnia) is fundamental to maintaining pH homeostasis. Developmental nicotine exposure has been shown to impair tadpole neuroventilatory responses to hypercapnia following 8,12 weeks of exposure. It is not clear, however, to what extent the timing of exposure during development and/or the duration over which the exposure takes place contribute to this impairment. Here, tadpoles were exposed to 30 ,g/L of nicotine for 3- or 10-week durations, either early or late in tadpole development. Correlates of tadpole lung neuroventilation were monitored during normocapnic (1.5% CO2) and hypercapnic (5% CO2) conditions of isolated brainstems. Preparations derived from early metamorphic tadpoles failed to increase lung neuroventilation in response to hypercapnia whether they had been exposed to nicotine for 3 or 10 weeks. Preparations derived from late metamorphic tadpoles failed to respond to hypercapnia after being exposed to nicotine for 10 weeks. These results suggest that both the developmental timing and duration of exposure are important when considering nicotine's effect on the hypercapnic neuroventilatory response. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 2009 [source]

Simulation of the dissolution of weathered versus unweathered limestone in carbonic acid solutions of varying strength

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2007
M. J. Thornbush
Abstract A simulation was undertaken within a climatic chamber to investigate limestone dissolution under varied carbonic acid (H2CO3) strengths as a possible analogue for future increases in atmospheric CO2 arising from global warming. Twenty-eight samples cut from a block of Bath (Box Hill) limestone from Somerville College, Oxford, which had been removed during restoration after 150 years in an urban environment, were weighed and placed in closed bottles of thin plastic containing varying concentrations of H2CO3. Half of the stone samples were derived from exposed surfaces of the stone block (weathered) while the others were obtained from the centre of the block on unexposed surfaces (unweathered). The purpose of this was to compare dissolution of previously weathered versus unweathered surfaces in strong (pH 4·73) versus weak (pH 6·43) solutions of H2CO3. A temperature of c. 19 °C was maintained within the chamber representing a plausible future temperature in Oxford for the year 2200 given current warming scenarios. The simulation lasted 25 days with a few stone samples being removed midway. Stone samples show reduced weight in all cases but one. There was greater dissolution of stone samples in a strong H2CO3 solution as conveyed by higher concentrations of total hardness and Ca2+ in the water samples as well as enhanced microscopic dissolution features identified using SEM. The simulation confirms that enhanced atmospheric CO2 under global warming, given adequate moisture, will accelerate dissolution rates particularly of newly replaced limestone building stones. However, previously weathered surfaces, such as those on historical stone exposed for a century or more, appear to be less susceptible to the effects of such increased rainfall acidity. Conservation techniques which remove weathered surfaces, such as stone cleaning, may accelerate future decay of historical limestone structures by increasing their susceptibility to dissolution. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Using Rock-Eval 6 pyrolysis for tracking fossil organic carbon in modern environments: implications for the roles of erosion and weathering

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2006
Yoann Copard
Abstract This work relates to the debate on the fossil organic carbon (FOC) input in modern environments and its possible implication for the carbon cycle, and suggests the use of Rock-Eval 6 pyrolysis as a relevant tool for tracking FOC in such environments. Considering that such a delivery is mainly due to supergene processes affecting the continental surface, we studied organic matter in different reservoirs such as bedrocks, alterites, soils and rivers in two experimental catchments at Draix (Alpes de Haute Provence, France). Samples were subjected to geochemical (Rock-Eval 6 pyrolysis) investigations and artificial bacterial degradations. After comparing the geochemical fingerprint of samples, geochemical markers of FOC were defined and tracked in the different reservoirs. Our results confirm the contribution of FOC in modern soils and rivers and display the various influences of weathering and erosional processes on the fate of FOC during its exchange between these pools. In addition, the contrasting behaviour of these markers upon the supergene processes has also highlighted the refractory or labile characters of the fossil organic matter (FOM). Bedrock to river fluxes, controlled by gully erosion, are characterized by a qualitative and quantitative preservation of FOM. Bedrock to alterite fluxes, governed by chemical weathering, are characterized by FOC mineralization without qualitative changes in deeper alterites. Alterite to soils fluxes, controlled by (bio)chemical weathering, are characterized by strong FOC mineralization and qualitative changes of FOM. Thus weathering and erosional processes induce different FOM evolution and affect the fate of FOC towards the global carbon cycle. In this study, gully erosion would involve maintenance of an ancient sink for the global carbon cycle, while (bio)chemical processes provide a source of CO2. Finally, this study suggests that Rock-Eval 6 pyrolysis can be considered as a relevant tool for tracking FOC in modern environments. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Cavitation versus Degassing: In Vitro Study of the Microbubble Phenomenon Observed During Echocardiography in Patients with Mechanical Prosthetic Cardiac Valves

ECHOCARDIOGRAPHY, Issue 7 2002
Grégoire Girod M.D.
Background: With the advent of second harmonic imaging in echocardiography, microbubbles have been observed during opening and closure of mechanical prosthetic valves. The single phenomenon of cavitation, an extremely short event described in the literature, cannot explain the persistence of microbubbles during several hundred milliseconds. Therefore, in vitro we reproduced two distinct phenomena created by a local depression occurring during the closure and/or opening of prosthetic valves: Cavitation and degassing. Methods: We used a water circuit system enriched with CO2 that passes through a Venturi tube in order to create variable pressure gradients. Three types of observations were performed: (1) the dimensions of the bubbles as a function of pressure, (2) calibration of the echocardiograph, and (3) comparison and illustrations of the difference between bubble formation by cavitation (vaporization) and degassing (liberation of CO2). Results: According to the different pressures exerted, the dimensions of the bubbles only vary by several microns, not measurable in practice. Second, the calibration of the echocardiograph reveals that the dimensions of the bubbles measured by ultrasound are greater by a factor of 1.75. Finally, the observed cavitation is a short phenomenon (several milliseconds) and happens under a great local pressure gradient. The degassing produces microbubbles lasting up to as long as > 1 second under much lower pressure. Conclusion: This in vitro study suggests that microbubbles observed during several hundred milliseconds after the opening of prosthetic cardiac valves are the result of degassing of CO2 in blood rather than a cavitation phenomenon as suggested in the literature. [source]

Atmospheric CO2 enrichment facilitates cation release from soil

ECOLOGY LETTERS, Issue 3 2010
L. Cheng
Ecology Letters (2010) 13: 284,291 Abstract Atmospheric CO2 enrichment generally stimulates plant photosynthesis and nutrient uptake, modifying the local and global cycling of bioactive elements. Although nutrient cations affect the long-term productivity and carbon balance of terrestrial ecosystems, little is known about the effect of CO2 enrichment on cation availability in soil. In this study, we present evidence for a novel mechanism of CO2 -enhancement of cation release from soil in rice agricultural systems. Elevated CO2 increased organic C allocation belowground and net H+ excretion from roots, and stimulated root and microbial respiration, reducing soil redox potential and increasing Fe2+ and Mn2+ in soil solutions. Increased H+, Fe2+, and Mn2+ promoted Ca2+ and Mg2+ release from soil cation exchange sites. These results indicate that over the short term, elevated CO2 may stimulate cation release from soil and enhance plant growth. Over the long-term, however, CO2 -induced cation release may facilitate cation losses and soil acidification, negatively feeding back to the productivity of terrestrial ecosystems. [source]

Species-specific responses to atmospheric carbon dioxide and tropospheric ozone mediate changes in soil carbon

ECOLOGY LETTERS, Issue 11 2009
Alan F. Talhelm
Abstract We repeatedly sampled the surface mineral soil (0,20 cm depth) in three northern temperate forest communities over an 11-year experimental fumigation to understand the effects of elevated carbon dioxide (CO2) and/or elevated phyto-toxic ozone (O3) on soil carbon (C). After 11 years, there was no significant main effect of CO2 or O3 on soil C. However, within the community containing only aspen (Populus tremuloides Michx.), elevated CO2 caused a significant decrease in soil C content. Together with the observations of increased litter inputs, this result strongly suggests accelerated decomposition under elevated CO2. In addition, an initial reduction in the formation of new (fumigation-derived) soil C by O3 under elevated CO2 proved to be only a temporary effect, mirroring trends in fine root biomass. Our results contradict predictions of increased soil C under elevated CO2 and decreased soil C under elevated O3 and should be considered in models simulating the effects of Earth's altered atmosphere. [source]

A review of nitrogen enrichment effects on three biogenic GHGs: the CO2 sink may be largely offset by stimulated N2O and CH4 emission

ECOLOGY LETTERS, Issue 10 2009
Lingli Liu
Abstract Anthropogenic nitrogen (N) enrichment of ecosystems, mainly from fuel combustion and fertilizer application, alters biogeochemical cycling of ecosystems in a way that leads to altered flux of biogenic greenhouse gases (GHGs). Our meta-analysis of 313 observations across 109 studies evaluated the effect of N addition on the flux of three major GHGs: CO2, CH4 and N2O. The objective was to quantitatively synthesize data from agricultural and non-agricultural terrestrial ecosystems across the globe and examine whether factors, such as ecosystem type, N addition level and chemical form of N addition influence the direction and magnitude of GHG fluxes. Results indicate that N addition increased ecosystem carbon content of forests by 6%, marginally increased soil organic carbon of agricultural systems by 2%, but had no significant effect on net ecosystem CO2 exchange for non-forest natural ecosystems. Across all ecosystems, N addition increased CH4 emission by 97%, reduced CH4 uptake by 38% and increased N2O emission by 216%. The net effect of N on the global GHG budget is calculated and this topic is reviewed. Most often N addition is considered to increase forest C sequestration without consideration of N stimulation of GHG production in other ecosystems. However, our study indicated that although N addition increased the global terrestrial C sink, the CO2 reduction could be largely offset (53,76%) by N stimulation of global CH4 and N2O emission from multiple ecosystems. [source]

The underestimated importance of belowground carbon input for forest soil animal food webs

ECOLOGY LETTERS, Issue 8 2007
Melanie M. Pollierer
Abstract The present study investigated the relative importance of leaf and root carbon input for soil invertebrates. Experimental plots were established at the Swiss Canopy Crane (SCC) site where the forest canopy was enriched with 13C depleted CO2 at a target CO2 concentration of c. 540 p.p.m. We exchanged litter between labelled and unlabelled areas resulting in four treatments: (i) leaf litter and roots labelled, (ii) only leaf litter labelled, (iii) only roots labelled and (iv) unlabelled controls. In plots with only 13C-labelled roots most of the soil invertebrates studied were significantly depleted in 13C, e.g. earthworms, chilopods, gastropods, diplurans, collembolans, mites and isopods, indicating that these taxa predominantly obtain their carbon from belowground input. In plots with only 13C-labelled leaf litter only three taxa, including, e.g. juvenile Glomeris spp. (Diplopoda), were significantly depleted in 13C suggesting that the majority of soil invertebrates obtain its carbon from roots. This is in stark contrast to the view that decomposer food webs are based on litter input from aboveground. [source]

Herbivore control of annual grassland composition in current and future environments

ECOLOGY LETTERS, Issue 1 2006
Halton A. Peters
Abstract Selective consumption by herbivores influences the composition and structure of a range of plant communities. Anthropogenically driven global environmental changes, including increased atmospheric carbon dioxide (CO2), warming, increased precipitation, and increased N deposition, directly alter plant physiological properties, which may in turn modify herbivore consumption patterns. In this study, we tested the hypothesis that responses of annual grassland composition to global changes can be predicted exclusively from environmentally induced changes in the consumption patterns of a group of widespread herbivores, the terrestrial gastropods. This was done by: (1) assessing gastropod impacts on grassland composition under ambient conditions; (2) quantifying environmentally induced changes in gastropod feeding behaviour; (3) predicting how grassland composition would respond to global-change manipulations if influenced only by herbivore consumption preferences; and (4) comparing these predictions to observed responses of grassland community composition to simulated global changes. Gastropod herbivores consume nearly half of aboveground production in this system. Global changes induced species-specific changes in plant leaf characteristics, leading gastropods to alter the relative amounts of different plant types consumed. These changes in gastropod feeding preferences consistently explained global-change-induced responses of functional group abundance in an intact annual grassland exposed to simulated future environments. For four of the five global change scenarios, gastropod impacts explained > 50% of the quantitative changes, indicating that herbivore preferences can be a major driver of plant community responses to global changes. [source]

Fire and the Miocene expansion of C4 grasslands

ECOLOGY LETTERS, Issue 7 2005
Jon E. Keeley
Abstract C4 photosynthesis had a mid-Tertiary origin that was tied to declining atmospheric CO2, but C4 -dominated grasslands did not appear until late Tertiary. According to the ,CO2 -threshold' model, these C4 grasslands owe their origin to a further late Miocene decline in CO2 that gave C4 grasses a photosynthetic advantage. This model is most appropriate for explaining replacement of C3 grasslands by C4 grasslands, however, fossil evidence shows C4 grasslands replaced woodlands. An additional weakness in the threshold model is that recent estimates do not support a late Miocene drop in pCO2. We hypothesize that late Miocene climate changes created a fire climate capable of replacing woodlands with C4 grasslands. Critical elements were seasonality that sustained high biomass production part of year, followed by a dry season that greatly reduced fuel moisture, coupled with a monsoon climate that generated abundant lightning-igniting fires. As woodlands became more open from burning, the high light conditions favoured C4 grasses over C3 grasses, and in a feedback process, the elevated productivity of C4 grasses increased highly combustible fuel loads that further increased fire activity. This hypothesis is supported by paleosol data that indicate the late Miocene expansion of C4 grasslands was the result of grassland expansion into more mesic environments and by charcoal sediment profiles that parallel the late Miocene expansion of C4 grasslands. Many contemporary C4 grasslands are fire dependent and are invaded by woodlands upon cessation of burning. Thus, we maintain that the factors driving the late Miocene expansion of C4 were the same as those responsible for maintenance of C4 grasslands today. [source]

Elevated CO2 and herbivory influence trait integration in Arabidopsis thaliana

ECOLOGY LETTERS, Issue 9 2004
M. Gabriela Bidart-Bouzat
Abstract We lack information on how elevated CO2, and its interaction with other factors like herbivory, affect levels and patterns of trait integration in plants. We experimentally tested the hypothesis that elevated CO2 disrupts and restructures functional associations among plant traits, in the selfing annual, Arabidopsis thaliana. We tested for these effects both in the presence and absence of herbivory by larvae of the diamondback moth, Plutella xylostella. Elevated CO2, both alone and combined with moth herbivory, modified integrated trait responses. In addition, integration under different environments was genotype-specific. These results imply that global changes in CO2 are likely to cause divergent evolutionary outcomes among populations of plants that differ in the initial structure of their quantitative genetic variation. [source]

Increase of atmospheric CO2 promotes phytoplankton productivity

ECOLOGY LETTERS, Issue 6 2004
Peter Schippers
Abstract It is usually thought that unlike terrestrial plants, phytoplankton will not show a significant response to an increase of atmospheric CO2. Here we suggest that this view may be biased by a neglect of the effects of carbon (C) assimilation on the pH and the dissociation of the C species. We show that under eutrophic conditions, productivity may double as a result of doubling of the atmospheric CO2 concentration. Although in practice productivity increase will usually be less, we still predict a productivity increase of up to 40% in marine species with a low affinity for bicarbonate. In eutrophic freshwater systems doubling of atmospheric CO2 may result in an increase of the productivity of more than 50%. Freshwaters with low alkalinity appeared to be very sensitive to atmospheric CO2 elevation. Our results suggest that the aquatic C sink may increase more than expected, and that nuisance phytoplankton blooms may be aggravated at elevated atmospheric CO2 concentrations. [source]

Scaling up evolutionary responses to elevated CO2: lessons from Arabidopsis

ECOLOGY LETTERS, Issue 5 2004
Joy K. Ward
Abstract Results from norm of reaction studies and selection experiments indicate that elevated CO2 will act as a selective agent on natural plant populations, especially for C3 species that are most sensitive to changes in atmospheric CO2 concentration. Evolutionary responses to CO2 may alter plant physiology, development rate, growth, and reproduction in ways that cannot be predicted from single generation studies. Moreover, ecological and evolutionary changes in plant communities will have a range of consequences at higher spatial scales and may cause substantial deviations from ecosystem level predictions based on short-term responses to elevated CO2. Therefore, steps need to be taken to identify the plant traits that are most likely to evolve at elevated CO2, and to understand how these changes may affect net primary productivity within ecosystems. These processes may range in scale from molecular and physiological changes that occur among genotypes at the individual and population levels, to changes in community- and ecosystem-level productivity that result from the integrative effects of different plant species evolving simultaneously. In this review, we (1) synthesize recent studies investigating the role of atmospheric CO2 as a selective agent on plants, (2) discuss possible control points during plant development that may change in response to selection at elevated CO2 with an emphasis at the primary molecular level, and (3) provide a quantitative framework for scaling the evolutionary effects of CO2 on plants in order to determine changes in community and ecosystem productivity. Furthermore, this review points out that studies integrating the effects of plant evolution in response to elevated CO2 are lacking, and therefore more attention needs be devoted to this issue among the global change research community. [source]

Is it simply getting worse?

ECONOMIC HISTORY REVIEW, Issue 4 2008
Agriculture, Swedish greenhouse gas emissions over 200 years
This paper challenges the idea that emissions of greenhouse gases simply increase over time with income. It adopts a 200-year perspective and includes the important flows of greenhouse gases related to agriculture, not just the CO2 from fossil fuels. The result is that the pattern of Swedish total greenhouse gas emissions over time resembles an N. In contrast, when only emissions from fossil fuels are counted, the pattern over time resembles an inverted U. Among the most important factors generating emissions in agriculture, forest management was especially important, but in addition, draining of wetlands for agriculture played a substantial role. [source]

Computation of locational and hourly maximum output of a distributed generator connected to a distribution feeder

ELECTRICAL ENGINEERING IN JAPAN, Issue 2 2009
Yasuhiro Hayashi
Abstract Recently, the total number of distributed generation such as photovoltaic generation systems and wind turbine generation systems connected to a distribution network has drastically increased. Distributed generation using renewable energy can reduce the distribution loss and emission of CO2. However, the distribution network with the distributed generators must be operated while maintaining the reliability of the power supply and power quality. In this paper, the authors propose a computational method to determine the maximum output of a distributed generator under operational constraints [(1) voltage limit, (2) line current capacity, and (3) no reverse flow to bank] at arbitrary connection points and hourly periods. In the proposed method, a three-phase iterative load flow calculation is applied to evaluate the above operational constraints. The three-phase iterative load flow calculation has two simple procedures: (Procedure 1) addition of load currents from the terminal node of the feeder to root one, and (Procedure 2) subtraction of voltage drop from the root node of the feeder to terminal one. In order to check the validity of the proposed method, numerical simulations are performed for a distribution system model. Furthermore, the characteristics of locational and hourly maximum output of a distributed generator connected to a distribution feeder are analyzed using several numerical examples. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 38,47, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20610 [source]

On the Initial Stages of Electrooxidation of Aqueous Maleic Acid on Bi-Doped PbO2

ELECTROANALYSIS, Issue 15 2007
Carlos Borras
Abstract Oxidation of maleic acid in aqueous solution on bismuth-doped lead oxide has been studied. The effects of hydrodynamic conditions on the oxidation rate have been identified. The number of electrons transferred during the initial stages of oxidation as well as the apparent heterogeneous rate constant was obtained from the combined analysis of rotating ring-disk currents and the decrease of concentration at constant potential, determined from UV-vis measurements. The number of electrons involved during electrochemical oxidation was found to be 12, indicating full mineralization to CO2, and the heterogeneous rate constant for oxidation at 1.6,V was 9.8×105,cm s,1. [source]

Ni(II)cyclam Catalyzed Reduction of CO2 , Towards a Voltammetric Sensor for the Gas Phase

ELECTROANALYSIS, Issue 18 2003
P. Jacquinot
Abstract The detection of CO2 in the gas phase is possible in presence of oxygen with an amalgamated Au-poly(tetrafluoroethylene) gas diffusion electrode and an internal electrolyte solution containing Ni(II)cyclam. For concentrations between 0.1 to 1% the electrochemical cell has a sensitivity of 3.58 mA %,1 and the detection limit is 500,ppm. In preliminary experiments at rotating disk electrodes the optimum pH-range was found to be between 3.5 to 6 and a selectivity ratio of the catalyst for CO2/H+ of 5,:,1 could be determined. The relationship between reduction current and the square root of the angular speed is linear, indicating that the electrochemical process is limited by diffusion of CO2. Tl and Pb are presented as alternative electrode materials at which the Ni(II)cyclam catalyzed reduction of CO2 can be observed. Problems arise from fouling effects at the sensing electrode and a non-linearity of the calibration plot at higher concentrations. [source]

Cycle analysis of low and high H2 utilization SOFCs/gas turbine combined cycle for CO2 recovery

ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 10 2008
Takuya Taniuchi
Abstract Global warming is mainly caused by CO2 emission from thermal power plants, which burn fossil fuel with air. One of the countermeasure technologies to prevent global warming is CO2 recovery from combustion flue gas and the sequestration of CO2 underground or in the ocean. SOFC and other fuel cells can produce high-concentration CO2, because the reformed fuel gas reacts with oxygen electrochemically without being mixed with air, or diluted by N2. Thus, we propose to operate the multistage SOFCs under high utilization of reformed fuel for obtaining high-concentration CO2. In this report, we have estimated the multistage SOFCs' performance considering H2 diffusion and the combined cycle efficiency of multistage SOFC/gas turbine/CO2 recovery power plant. The power generation efficiency of our CO2 recovery combined cycle is 68.5% and the efficiency of conventional SOFC/GT cycle is 57.8% including the CO2 recovery amine process. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 91(10): 38,45, 2008; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/ecj.10165 [source]

Identification of diphenhydramine metabolites in human urine by capillary electrophoresis-ion trap-mass spectrometry

ELECTROPHORESIS, Issue 10-11 2004
Andrea Baldacci
Abstract The identification of diphenhydramine (DH) metabolites that are frequently observed in the capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) analyses of alkaline liquid/liquid and solid-phase extracts of patient urines is demonstrated. Having standards for DH and diphenhydramine- N -oxide (DHNO), the presence of these two compounds could be confirmed in urines that were collected overnight after administration of 25 mg DH chloride. Using CZE coupled to ion-trap mass spectrometry (CE-MSn) with positive electrospray ionization and an acetate buffer at pH 5.6, the [M+H]+ ions of DH (m/z = 256), DHNO (m/z = 272), and nordiphenhydramine (NDH, m/z = 242) and their fragmentation to a common m/z 167 product ion (diphenylcarbinol moiety) was monitored. The data indicate that all three compounds are cations in an acidic environment, the migration order being NDH, DH, and DHNO. Data obtained under negative electrospray ionization conditions suggest the presence of diphenylmethoxyacetic acid-glycine amide ([M-H], ion of m/z 298 and fragmentation to m/z 254, loss of CO2), a metabolite that could tentatively be assigned to a characteristic peak observed in the MEKC electropherogram at alkaline pH. The data presented in this paper illustrate the value of using CE-MSn for identification of urinary drug metabolites for which no standards are available. [source]

Acclimation Strategy of a Biohydrogen Producing Population in a Continuous-Flow Reactor with Carbohydrate Fermentation

ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2006
Q. Ren
Abstract Poor startup of biological hydrogen production systems can cause an ineffective hydrogen production rate and poor biomass growth at a high hydraulic retention time (HRT), or cause a prolonged period of acclimation. In this paper a new startup strategy was developed in order to improve the enrichment of the hydrogen-producing population and the efficiency of hydrogen production. A continuously-stirred tank reactor (CSTR) and molasses were used to evaluate the hydrogen productivity of the sewage sludge microflora at a temperature of 35,°C. The experimental results indicated that the feed to microorganism ratio (F/M ratio) was a key parameter for the enrichment of hydrogen producing sludge in a continuous-flow reactor. When the initial biomass was inoculated with 6.24,g of volatile suspended solids (VSS)/L, an HRT of 6,h, an initial organic loading rate (OLR) of 7.0,kg chemical oxygen demand (COD)/(m3,×,d) and an feed to microorganism ratio (F/M) ratio of about 2,3,g COD/(g of volatile suspended solids (VSS) per day) were maintained during startup. Under these conditions, a hydrogen producing population at an equilibrium state could be established within 30,days. The main liquid fermentation products were acetate and ethanol. Biogas was composed of H2 and CO2. The hydrogen content in the biogas amounted to 47.5,%. The average hydrogen yield was 2.01,mol/mol hexose consumed. It was also observed that a special hydrogen producing population was formed when this startup strategy was used. It is supposed that the population may have had some special metabolic pathways to produce hydrogen along with ethanol as the main fermentation products. [source]

Effects of elevated CO2 associated with maize on multiple generations of the cotton bollworm, Helicoverpa armigera

ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2010
Jin Yin
Abstract Under elevated environmental carbon dioxide (CO2), leaf chewers tend to compensate for decreased leaf nutritional quality with increased consumption; mortality and development times also increase and cause a reduction in the fitness of leaf chewers. However, the effect of elevated CO2 on multiple successive generations of these and other insects is not well understood. Furthermore, information about the direct effects of increased environmental CO2 on developmental time and consumption of herbivores is lacking. In this paper, we tested the hypothesis that cascade effects of elevated CO2 through plants, rather than the direct effects of elevated CO2, are the main factors decreasing the fitness of cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae). We used two series of experiments to quantify the growth, development, and consumption of H. armigera fed on an artificial diet or C4 plants (maize) grown under two CO2 levels (ambient vs. double ambient). In the first series of experiments, elevated CO2 had no effect on the population abundance or individual consumption for three successive generations of cotton bollworms fed on an artificial diet. In the second series of experiments, elevated CO2 reduced population abundance of cotton bollworm larvae for two successive generations when they were fed maize milky grains. The specific effects were longer larval duration, lower fecundity, and decreased rm of cotton bollworms. Furthermore, elevated CO2 increased individual consumption when cotton bollworm was fed maize milky grains for two successive generations and decreased the population's total consumption in the first generation but increased it in the second generation. The results from this study indicate that: (1) The effects of elevated CO2 on three successive generations of cotton bollworm fed on artificial diet were weak, or even non-existent, and (2) elevated CO2 increased the consumption when cotton bollworm were fed maize. Our study also suggests that the damage inflicted by cotton bollworm on maize (a C4 plant) will be seriously affected by the increases in atmospheric CO2, which is unlike our previous results for spring wheat (a C3 plant). [source]