scholarly journals Egg clutch dehydration induces early hatching in red-eyed treefrogs, Agalychnis callidryas

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3549 ◽  
Author(s):  
María José Salica ◽  
James R. Vonesh ◽  
Karen M. Warkentin
Keyword(s):  
Egg Mortality ◽  
Agalychnis Callidryas ◽  
Independent Origin ◽  
Rapid Changes ◽  
Dry Conditions ◽  
Egg Diameter ◽  
Over Time

Terrestrial eggs have evolved repeatedly in tropical anurans exposing embryos to the new threat of dehydration. Red-eyed treefrogs, Agalychnis callidryas, lay eggs on plants over water. Maternally provided water allows shaded eggs in humid sites to develop to hatching without rainfall, but unshaded eggs and those in less humid sites can die from dehydration. Hatching responses of amphibian eggs to dry conditions are known from two lineages with independent origins of terrestrial eggs. Here, we experimentally tested for dehydration-induced early hatching in another lineage (Agalychnis callidryas, Phyllomedusidae), representing a third independent origin of terrestrial eggs. We also investigated how dehydration affected egg and clutch structure, and egg mortality. We collected clutches from a pond in Gamboa, Panama, and randomly allocated them to wet or dry treatments at age 1 day. Embryos hatched earlier from dry clutches than from wet clutches, accelerating hatching by ∼11%. Clutch thickness and egg diameter were affected by dehydration, diverging between treatments over time. Meanwhile, mortality in dry clutches was six-fold higher than in control clutches. With this study, early hatching responses to escape mortality from egg dehydration are now known from three anuran lineages with independent origins of terrestrial eggs, suggesting they may be widespread. Further studies are needed to understand how terrestrial amphibian eggs can respond to, or will be affected by, rapid changes in climate over the next decades.

ICT and Knowledge Management Systems

2011 ◽  
pp. 1042-1050 ◽  
Author(s):  
Irma Becerra-Fernandez ◽  
Rajiv Sabherwal
Keyword(s):  
Knowledge Management ◽  
Knowledge Sharing ◽  
Knowledge Management Systems ◽  
Complex Processes ◽  
Rapid Changes ◽  
Growth Of Knowledge ◽  
Information And Communication ◽  
Accelerated Growth ◽  
Structural Mechanisms ◽  
Over Time

Rapid changes in the field of knowledge management (KM) have to a great extent resulted from the dramatic progress we have witnessed in the field of information and communication technology. ICT allows the movement of information at increasing speeds and efficiencies, and thus facilitates sharing as well as accelerated growth of knowledge. For example, computers capture data from measurements of natural phenomena, and then quickly manipulate the data to better understand the phenomena they represent. Increased computer power at lower prices enables the measurement of increasingly complex processes, which we possibly could only imagine before. Thus, ICT has provided a major impetus for enabling the implementation of KM applications. Moreover, as learning has accrued over time in the area of social and structural mechanisms, such as through mentoring and retreats that enable effective knowledge sharing, it has made it possible to develop KM applications that best leverage these improved mechanisms by deploying sophisticated technologies.

scholarly journals Lack of Evidence for Impact of the European White Birch, Betula pendula, on the Hydrology of Wainfleet Bog, Ontario

2003 ◽  
Vol 117 (3) ◽  
pp. 393
Author(s):  
Joshua Diamond ◽  
Mark Browning ◽  
Andrew Williams ◽  
John Middleton
Keyword(s):  
Invasive Species ◽  
Water Table ◽  
Significant Relationship ◽  
Repeated Measures ◽  
Betula Pendula ◽  
White Birch ◽  
Native Flora ◽  
Dry Conditions ◽  
Analysis Of Results ◽  
Over Time

Over time peat harvesting and human encroachment have devastated the hydrology of Wainfleet Bog. Disturbances caused by human activities have rendered the bog ecosystem vulnerable to an influx of invasive species. The European White Birch (Betula pendula) has contributed to the degradation of the Wainfleet Bog. The disrupted hydrology has allowed for the development of dry conditions that have enabled B. pendula to take over habitats that were once dominated by native flora. To determine whether B. pendula was depressing the water table through evapotranspiration, we examined water table levels (March 1998 to July 1999) and vegetative data from 15 well stations. Analysis of results using a Repeated Measures Statistic Design failed to demonstrate a significant relationship between the presence of B. pendula and water table levels at Wainfleet Bog.

scholarly journals Uptake of gaseous formaldehyde by soil surfaces: a combination of adsorption/desorption equilibrium and chemical reactions

2016 ◽  
Author(s):  
Guo Li ◽  
Hang Su ◽  
Xin Li ◽  
Uwe Kuhn ◽  
Hannah Meusel ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Chemical Reactions ◽  
High Surface ◽  
Oh Radicals ◽  
Ambient Conditions ◽  
Complex Process ◽  
Dry Conditions ◽  
Gaseous Formaldehyde ◽  
Adsorption Desorption ◽  
Over Time

Abstract. Gaseous formaldehyde (HCHO) is an important precursor of OH radicals and a key intermediate molecule in the oxidation of atmospheric volatile organic compounds (VOCs). Budget analyses reveal large discrepancies between modeled and observed HCHO concentrations in the atmosphere. Here, we investigate the interactions of gaseous HCHO with soil surfaces through coated-wall flow tube experiments applying atmospherically relevant HCHO concentrations of ~ 10 to 40 ppbv. For the determination of uptake coefficients (γ), we provide a Matlab code to account for the diffusion correction under laminar flow conditions. Under dry conditions (relative humidity = 0 %), an initial γ of (1.1 ± 0.05) × 10−4 is determined, which gradually drops to (5.5 ± 0.4) × 10−5 after 8-hour experiments. Experiments under wet conditions show a smaller γ that drops faster over time until reaching a plateau. The drop of γ with increasing relative humidity and over time can both be explained by the adsorption theory in which high surface coverage leads to a reduced uptake rate. The fact that γ stabilizes at a non-zero plateau suggests the involvement of irreversible chemical reactions. Further back-flushing experiments show that two thirds of the adsorbed HCHO can be re-emitted into the gas phase while the residual is retained by the soil. This partial reversibility confirms that HCHO uptake by soil is a complex process involving both adsorption/desorption and chemical reactions which must be considered in trace gas exchange (emission or deposition) at the atmosphere-soil interface. Our results suggest that soil and soil-derived airborne particles can either act as a source or a sink for HCHO, depending on ambient conditions and HCHO concentrations.

Human Factors Assessment of Pavement Marking Retroreflectivity in Simulated Rain and Dry Conditions

2021 ◽  
pp. 036119812110111
Author(s):  
Timothy P. Barrette ◽  
Adam M. Pike
Keyword(s):  
Human Factors ◽  
Subjective Rating ◽  
Detection Distance ◽  
Pavement Markings ◽  
Dry Conditions ◽  
Simulated Rain ◽  
Pavement Marking ◽  
Over Time

Pavement marking retroreflectivity standards are typically developed with dry conditions in mind, however, driving at night during rainfall is seemingly one of the most challenging and stressful situations for a driver. Furthermore, existing research indicates continuous wet retroreflectivity is relatively weakly correlated with dry retroreflectivity and deteriorates differently over time, leading to the obvious conclusion that dry retroreflectivity standards alone are not enough to ensure that pavement markings meet the needs of drivers across the breadth of roadway conditions that may occur. Consequently, developing standards for minimum continuous wet retroreflectivity for new installations and for maintenance purposes represents an important area for research. This study aims to develop new installation and maintenance values for continuous wet retroreflectivity based on a multifaceted, closed-course study of detectability of pavement markings in simulated rain and dry conditions. A series of 20 pavement marking samples was evaluated in relation to detection distance and subjective rating. The results of the study indicated that pavement markings need to be maintained at a continuous wet retroreflectivity value of 50 mcd/m2/lux based on a participant pool that skewed older in age, but that likely represents something close to the 85th-percentile driver. Additional salient findings included observed wet retroreflectivity loss in the existing literature of approximately 7% per month, as well as the maximum preview time in simulated rain conditions being substantially lower than in dry conditions.

Fecundity of Nephrops norvegicus from the Irish Sea

2009 ◽  
Vol 89 (6) ◽  
pp. 1181-1188 ◽  
Author(s):  
N. McQuaid ◽  
R.P. Briggs ◽  
D. Roberts
Keyword(s):  
Incubation Period ◽  
Significant Variation ◽  
Carapace Length ◽  
Irish Sea ◽  
Female Size ◽  
Potential Fecundity ◽  
Mature Ovary ◽  
The Irish Sea ◽  
Egg Diameter ◽  
Over Time

Potential fecundity, number of oocytes in the mature ovary, and realized fecundity, number of eggs extruded and attached to the pleopods of female Nephrops, caught at the start of the incubation period were estimated for females from the eastern and western Irish Sea grounds. Potential fecundity was found to differ significantly between eastern and western Irish Sea stocks, while realized fecundity did not differ between areas. Inter-year comparison of realized fecundity, and effective fecundity (the number of mature eggs on the pleopods of females at the end of the incubation period) in the western Irish Sea stocks revealed no significant variation over time. Egg loss during the transition from oocytes in the ovary to mature eggs increased with female size, ranging from 40% at 25 mm carapace length (CL) to 65% at 40 mm CL. No relationship was found between egg diameter or volume and female size.

scholarly journals Quantitative Estimation of the Viability of Toxoplasma gondii Oocysts in Soil

2012 ◽  
Vol 78 (15) ◽  
pp. 5127-5132 ◽  
Author(s):  
Maud Lélu ◽  
Isabelle Villena ◽  
Marie-Laure Dardé ◽  
Dominique Aubert ◽  
Régine Geers ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Life Expectancy ◽  
Animal Species ◽  
Quantitative Estimation ◽  
Soil Samples ◽  
Content Type ◽  
Stable Temperature ◽  
Dry Conditions ◽  
Microscopic Counting ◽  
Over Time

ABSTRACTToxoplasma gondiioocysts spread in the environment are an important source of toxoplasmosis for humans and animal species. Although the life expectancy of oocysts has been studied through the infectivity of inoculated soil samples, the survival dynamics of oocysts in the environment are poorly documented. The aim of this study was to quantify oocyst viability in soil over time under two rain conditions. Oocysts were placed in 54 sentinel chambers containing soil and 18 sealed water tubes, all settled in two containers filled with soil. Containers were watered to simulate rain levels of arid and wet climates and kept at stable temperature for 21.5 months. At nine sampling dates during this period, we sampled six chambers and two water tubes. Three methods were used to measure oocyst viability: microscopic counting, quantitative PCR (qPCR), and mouse inoculation. In parallel, oocysts were kept refrigerated during the same period to analyze their detectability over time. Microscopic counting, qPCR, and mouse inoculation all showed decreasing values over time and highly significant differences between the decreases under dry and damp conditions. The proportion of oocysts surviving after 100 days was estimated to be 7.4% (95% confidence interval [95% CI] = 5.1, 10.8) under dry conditions and 43.7% (5% CI = 35.6, 53.5) under damp conditions. The detectability of oocysts by qPCR over time decreased by 0.5 cycle threshold per 100 days. Finally, a strong correlation between qPCR results and the dose infecting 50% of mice was found; thus, qPCR results may be used as an estimate of the infectivity of soil samples.

scholarly journals Uptake of gaseous formaldehyde by soil surfaces: a combination of adsorption/desorption equilibrium and chemical reactions

2016 ◽  
Vol 16 (15) ◽  
pp. 10299-10311 ◽  
Author(s):  
Guo Li ◽  
Hang Su ◽  
Xin Li ◽  
Uwe Kuhn ◽  
Hannah Meusel ◽  
...  
Keyword(s):  
Chemical Reactions ◽  
High Surface ◽  
Oh Radicals ◽  
Ambient Conditions ◽  
Complex Process ◽  
Dry Conditions ◽  
Gaseous Formaldehyde ◽  
Adsorption Desorption ◽  
Over Time

Abstract. Gaseous formaldehyde (HCHO) is an important precursor of OH radicals and a key intermediate molecule in the oxidation of atmospheric volatile organic compounds (VOCs). Budget analyses reveal large discrepancies between modeled and observed HCHO concentrations in the atmosphere. Here, we investigate the interactions of gaseous HCHO with soil surfaces through coated-wall flow tube experiments applying atmospherically relevant HCHO concentrations of  ∼  10 to 40 ppbv. For the determination of uptake coefficients (γ), we provide a Matlab code to account for the diffusion correction under laminar flow conditions. Under dry conditions (relative humidity  =  0 %), an initial γ of (1.1 ± 0.05)  ×  10−4 is determined, which gradually drops to (5.5 ± 0.4)  ×  10−5 after 8 h experiments. Experiments under wet conditions show a smaller γ that drops faster over time until reaching a plateau. The drop of γ with increasing relative humidity as well as the drop over time can be explained by the adsorption theory in which high surface coverage leads to a reduced uptake rate. The fact that γ stabilizes at a non-zero plateau suggests the involvement of irreversible chemical reactions. Further back-flushing experiments show that two-thirds of the adsorbed HCHO can be re-emitted into the gas phase while the residual is retained by the soil. This partial reversibility confirms that HCHO uptake by soil is a complex process involving both adsorption/desorption and chemical reactions which must be considered in trace gas exchange (emission or deposition) at the atmosphere–soil interface. Our results suggest that soil and soil-derived airborne particles can either act as a source or a sink for HCHO, depending on ambient conditions and HCHO concentrations.

scholarly journals The Role of Coping Skills for Developing Resilience Among Children and Adolescents

2021 ◽  
pp. 345-368
Author(s):  
Tammie Ronen
Keyword(s):  
Young People ◽  
Children And Adolescents ◽  
Natural Environments ◽  
Loved One ◽  
The Past ◽  
Rapid Changes ◽  
Secure Environment ◽  
The Individual ◽  
Over Time

AbstractChildren and adolescents experience rapid changes due to development and growth processes, thereby necessitating adaptation and flexibility. In addition, young people also often face environmental crises or traumas, human-made catastrophes, or individual (chronic illness) or family (parent divorce, death of a loved one) crises. In the past, to facilitate young people’s adaptation to change, major aims of parents, teachers, and therapists focused on protecting children and adolescents from harm and helping them grow up in a secure environment. Over time, modern life and the influence of the positive psychology orientation have led to a shift in those aims, which now focus more on helping young people feel happy, flourish, and use their own strengths. A key element in making this process of adaptation to change successful is resilience. This chapter deals with the effects of changes, crises, and traumas on children and adolescents, while focusing on the importance of resilience at the individual, family, and environmental levels. This approach directs adaptation to change efforts towards the present rather than towards the past, thereby meeting the important need of treating children and adolescents who have experienced crisis and trauma by imparting them with skills for better coping today in their major natural environments.

Economics of the Ed Tech Revolution

2017 ◽  
Vol 59 (4) ◽  
pp. 49-55 ◽  
Author(s):  
Richard K. Lyons
Keyword(s):  
Artificial Intelligence ◽  
Machine Learning ◽  
Network Effects ◽  
Education Technology ◽  
Increasing Returns ◽  
Durable Good ◽  
Rapid Changes ◽  
Over Time ◽  
The Way

Rapid changes in technology—including advances in augmented and artificial intelligence, machine learning, and mobile—are paving the way for significant changes not only in the channels through which education is delivered but in how education itself is structured. This article identifies eight ways in which education technology can change how learning is facilitated and who will facilitate that learning. Basic economic principles then provide a framework for thinking about how these changes will be embedded over time as education increasingly becomes a durable good providing increasing returns through network effects.

Gas in Electricity Generation

1995 ◽  
Vol 13 (2-3) ◽  
pp. 149-157
Author(s):  
K. Devine
Keyword(s):  
Electricity Generation ◽  
Electricity Demand ◽  
Generation System ◽  
Thermal Generation ◽  
Change Over Time ◽  
Hydrological Conditions ◽  
Long Run ◽  
Rapid Changes ◽  
Gas Supply ◽  
Over Time

Gas is New Zealand's major thermal fuel for electricity generation. This paper describes what influences the volumes of gas burnt by ECNZ, and forecasts future gas demands for electricity generation. It also reviews the uncertainties associated with these forecasts and likely competition in building new electricity generating stations and outlines the strategy now being formulated to accommodate them. Because ECNZ's generation system is hydro-based, relatively small rapid changes in hydrological conditions can significantly affect the amount of gas used. This situation will change over time with major increases in thermal generation likely to be needed over the next 20 years. However, there are considerable uncertainties on gas supply and electricity demand levels in the long run, which will complicate investment and fuel decisions.

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