Relationship Between Thermal Stability and Summer Oxygen Depletion in a Prairie Pothole Lake

1980 ◽  
Vol 37 (9) ◽  
pp. 1433-1438 ◽  
Author(s):  
M. H. Papst ◽  
J. A. Mathias ◽  
J. Barica
Keyword(s):  
Thermal Stability ◽  
Air Temperature ◽  
Algal Biomass ◽  
Thermal Instability ◽  
Oxygen Depletion ◽  
Prairie Pothole ◽  
Night Time ◽  
Algae Blooms ◽  
Principal Factors ◽  
Prairie Lakes

Periods of summer oxygen depletion (summerkill), occurring in shallow prairie lakes, are dependent on the collapse of algae blooms but are not an obligatory result of the collapse. A period of thermal instability following this bloom collapse, or coincidental with it, is a necessary requirement. Wind stress and night-time air temperature are the principal factors determining the degree of thermal stability. These findings explain the speed with which oxygen depletion can occur, that the occurrence of algal biomass collapses without severe oxygen depletion (partial collapses), and the correlation between the occurrence of periods of lake oxygen depletion and changing weather conditions.Key words: lake, summerkill, anoxia, mixing, oxygen depletion, thermal stability, weather, Aphanizomenon

Two-terminal vertical thyristor using Schottky contact emitter to improve thermal instability

Nano Futures ◽  
2021 ◽  
Author(s):  
Min-Won Kim ◽  
Ji-Hun Kim ◽  
Jun-Seong Park ◽  
Byoung-Seok Lee ◽  
Sangdong Yoo ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Work Function ◽  
Thermal Instability ◽  
Schottky Contact ◽  
Memory Cell ◽  
Cross Point ◽  
Operation Temperature ◽  
Metal Work Function ◽  
Metal Work ◽  
Contact Metal

Abstract In a two-terminal-electrode vertical thyristor, the latch-up and latch-down voltages are decreased when the memory operation temperature of the memory cells increases, resulting in a severe reliability issue (i.e., thermal instability). This study fundamentally solves the thermal instability of a vertical-thyristor by achieving a cross-point memory-cell array using a vertical-thyristor with a structure of vertical n++-emitter, p+-base, n+-base, and p++-emitter. The vertical-thyristor using a Schottky contact metal emitter instead of an n++-Si emitter significantly improves the thermal stability between 293 and 373 K. Particularly, the improvement degree of the thermal stability is increased significantly with the use of the Schottky contact metal work function. Because the thermal instability (i.e., degree of latch-up voltage decrement vs. memory operation temperature) decreases with an increase in the Schottky contact metal work function, the dependency of the forward current density between the Schottky contact metal and p+-Si based on the memory operation temperature reduces with increase in the Schottky contact metal work function. Consequently, a higher Schottky contact metal work function produces a higher degree of improvement in the thermal stability, i.e., W (4.50 eV), Ti (4.33 eV), Ta (4.25 eV), and Al (4.12 eV). Further research on the fabrication process of a Schottky contact metal emitter vertical-thyristor is essential for the fabrication of a 3-D cross-point memory-cell.

scholarly journals Some like it hot: A differential response to changing temperatures by the malaria vectors Anopheles funestus and An. gambiae s.l.

2016 ◽  
Author(s):  
Jacques D Charlwood
Keyword(s):  
Air Temperature ◽  
Light Trap ◽  
Anopheles Funestus ◽  
Malaria Vectors ◽  
Effect Of Temperature ◽  
Night Time ◽  
Environmental Correlations ◽  
Air Temperatures ◽  
Soil Temperatures ◽  
Gravid Females

Background: With the possible implications of global warming, the effect of temperature on the dynamics of malaria vectors in Africa has become a subject of increasing interest. Information from the field is, however, relatively sparse. We describe the effect of ambient temperature over a five-year period on the dynamics of An. funestus and An. gambiae s.l., collected from a single village in southern Mozambique where temperatures varied from a night-time minimum of 6oC in the cool season to a daytime maximum of 35oC in the hot season. Results: Mean daily air temperatures varied from 34o C to 20oC and soil temperatures varied from 26 o C to 12 o C. Diurnal variation was greatest in the cooler months of the year and were greater in air temperatures than soil temperatures. During the study 301, 705 female An. funestus were collected in 6043 light-trap collections, 161, 466 in 7397 exit collections and 16, 995 in 1315 resting collections. The equivalent numbers for An. gambiae s.l. are 72, 475 in light-traps, 33, 868 in exit collections and 5, 333 from indoor resting collections. Numbers of mosquito were greatest in the warmer months. Numbers of An. gambiae s.l. went through a one hundredfold change (from a mean of 0.14 mosquitoes a night to 14) whereas numbers of An. funestus merely doubled (from a mean of 20 to 40 a night). The highest environmental correlations and mosquito numbers were between mean air temperature (r2 = 0.52 for An. funestus and 0.77 for An. gambiae s.l.). Numbers of mosquito collected were not related to rainfall with lags of up to four weeks. Numbers of both gravid and unfed An. gambiae complex females in exit collections continued to increase at all temperatures recorded but gravid females of An. funestus decreased at temperatures above 28oC. Overall the numbers of gravid and unfed An. funestus collected in exit collections were not correlated (p = 0.07). For an unknown reason the number of An. gambiae s.l. fell below monitoring thresholds during the study. Conclusions: Mean air temperature was the most important environmental parameter affecting both vectors in this part of Mozambique. Numbers of An. gambiae s.l. increased at all temperatures recorded whilst An. funestus appeared to be adversely affected by temperatures of 28oC and above. These differences may influence the distribution of the vectors as the planet warms.

scholarly journals The influence of the forest on night-time snow surface temperature

2001 ◽  
Vol 32 ◽  
pp. 217-222 ◽  
Author(s):  
Peter Höller
Keyword(s):  
Surface Temperature ◽  
Open Field ◽  
Air Temperature ◽  
Forest Canopy ◽  
Small Range ◽  
Snow Surface ◽  
Net Radiation ◽  
Night Time ◽  
Near Surface ◽  
Snow Surface Temperature

AbstractSnow surface temperature (Ts) plays an important role in the formation of surface hoar or near-surface faceted crystals The goal of this study was to obtain detailed information on Ts in different forest stands nelr the timberline. The investigations were conducted during clear nights and showed that the snow surface temperature is influenced very strongly by the forest canopy. While the air temperature was very similar on the different experimental sites, Ts was higher in the forest than in the open field; on the south-facing slope the difference between the forest and the open field was 3–4.5°C, and on the north-facing slope approximately 3–7°C. Taking into account that εair is 0.7 and εtree is 0.94, the incoming radiation (I ↓) for the different experimental sites was calculated by the equation of Brunt (the canopy density was estimated using photographs taken with an 8 mm fish-eye). To calculate Ts, air temperature and averaged values of the net radiation (because the net radiation (I) has only a small range of variation during clear nights) were used. The results show that the calculated values were higher than the measured values (by approximately 2°C). However, a better correlation was found by using lower values of the emissivity (εair0.67 and εtree0.91).

Factors Controlling Oxygen Depletion in Ice-Covered Lakes

1980 ◽  
Vol 37 (2) ◽  
pp. 185-194 ◽  
Author(s):  
Jack A. Mathias ◽  
Jan Barica
Keyword(s):  
Volume Ratio ◽  
Lake Management ◽  
Eddy Diffusion ◽  
Oxygen Depletion ◽  
Eutrophic Lakes ◽  
Experimental Lakes Area ◽  
Lake Volume ◽  
Basin Morphometry ◽  
Depletion Rate ◽  
Prairie Lakes

Winter oxygen depletion rates from four sets of Canadian lakes (prairie, southeastern Ontario, Arctic, and Experimental Lakes Area) differing in morphometry and trophic state, were analyzed. An inverse relationship was found between oxygen depletion rate and mean depth. The effect of lake trophic status on oxygen depletion rate was demonstrable after the influence of basin morphometry was removed by regression of oxygen depletion rate against the sediment area: lake volume ratio. The sediments of eutrophic lakes consumed oxygen about 3 times faster (0.23 g∙m−2∙d−1) than those of oligotrophic lakes (0.08 g∙m−2∙d−1), but water column respiration was about the same (0.01 g∙m−3∙d−1) for both groups of lakes. Data from prairie lakes showed that the winter oxygen consumption was limited by oxygen supply below an average whole-lake oxygen concentration of 3.8 mg∙L−1. The rate of eddy diffusion near the sediments in ice-covered prairie lakes was 3.72 ± 1.41 × 10−3 cm2∙s−1. Implications for lake management during the winter are discussed.Key words: oxygen, depletion, respiration, lakes, ice-covered, winter, sediments, model, consumption

Quantifying heating biases in marine air temperature observations, ~1790 - present

2021 ◽  
Author(s):  
Thomas Cropper ◽  
Elizabeth Kent ◽  
David Berry ◽  
Richard Cornes ◽  
Beatriz Recinos-Rivas
Keyword(s):  
Air Temperature ◽  
Diurnal Cycle ◽  
Surface Air Temperature ◽  
Night Time ◽  
Data Set ◽  
Near Surface ◽  
Marine Surface ◽  
Heating Model ◽  
Marine Air

<p>Accurate, long-term time series of near-surface air temperature (AT) are the fundamental datasets on which the magnitude of anthropogenic climate change is scientifically and societally addressed. Across the ocean, these (near-surface) climate records use Sea Surface Temperature (SST) instead of Marine Air Temperature (MAT) and blend the SST and AT over land to create datasets. MAT has often been overlooked as a data choice as daytime MAT observations from ships are known to contain warm biases due to the storage of accumulated solar energy. Two recent MAT datasets, CLASSnmat (1881 – 2019) and UAHNMAT (1900 – 2018), both use night-time MAT observations only. Daytime MAT observations in the International Comprehensive Ocean–Atmosphere Data Set (ICOADS) account for over half of the MAT observations in ICOADS, and this proportion increases further back in time (i.e. pre-1850s). If long-term MAT records over the ocean are to be extended, the use of daytime MAT is vital.</p><p> </p><p>To adjust for the daytime MAT heating bias, and apply it to ICOADS, we present the application of a physics-based model, which accounts for the accumulated energy storage throughout the day. As the ‘true’ diurnal cycle of MAT over the ocean has not been, to-date, adequately quantified, our approach also removes the diurnal cycle from ICOADS observations and generates a night-time equivalent MAT for all observations. We fit this model to MAT observations from groups of ships in ICOADS that share similar heating biases and metadata characteristics. This enables us to use the empirically derived coefficients (representing the physical energy transfer terms of the heating model) obtained from the fit for use in removal of the heating bias and diurnal cycle from ship-based MAT observations throughout ICOADS which share similar characteristics (i.e. we can remove the diurnal cycle from a ship which only reports once daily at noon). This adjustment will create an MAT record of night-time-equivalent temperatures that will enable an extension of the marine surface AT record back into the 18<sup>th</sup> century.</p>

scholarly journals Net ecosystem carbon exchange of a dry temperate eucalypt forest

2017 ◽  
Vol 14 (16) ◽  
pp. 3781-3800 ◽  
Author(s):  
Nina Hinko-Najera ◽  
Peter Isaac ◽  
Jason Beringer ◽  
Eva van Gorsel ◽  
Cacilia Ewenz ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Air Temperature ◽  
Carbon Exchange ◽  
Night Time ◽  
Annual Variability ◽  
Eucalypt Forest ◽  
Ecosystem Carbon ◽  
Environmental Controls ◽  
Net Ecosystem Carbon Exchange ◽  
Ecosystem Carbon Exchange

Abstract. Forest ecosystems play a crucial role in the global carbon cycle by sequestering a considerable fraction of anthropogenic CO2, thereby contributing to climate change mitigation. However, there is a gap in our understanding about the carbon dynamics of eucalypt (broadleaf evergreen) forests in temperate climates, which might differ from temperate evergreen coniferous or deciduous broadleaved forests given their fundamental differences in physiology, phenology and growth dynamics. To address this gap we undertook a 3-year study (2010–2012) of eddy covariance measurements in a dry temperate eucalypt forest in southeastern Australia. We determined the annual net carbon balance and investigated the temporal (seasonal and inter-annual) variability in and environmental controls of net ecosystem carbon exchange (NEE), gross primary productivity (GPP) and ecosystem respiration (ER). The forest was a large and constant carbon sink throughout the study period, even in winter, with an overall mean NEE of −1234 ± 109 (SE) g C m−2 yr−1. Estimated annual ER was similar for 2010 and 2011 but decreased in 2012 ranging from 1603 to 1346 g C m−2 yr−1, whereas GPP showed no significant inter-annual variability, with a mean annual estimate of 2728 ± 39 g C m−2 yr−1. All ecosystem carbon fluxes had a pronounced seasonality, with GPP being greatest during spring and summer and ER being highest during summer, whereas peaks in NEE occurred in early spring and again in summer. High NEE in spring was likely caused by a delayed increase in ER due to low temperatures. A strong seasonal pattern in environmental controls of daytime and night-time NEE was revealed. Daytime NEE was equally explained by incoming solar radiation and air temperature, whereas air temperature was the main environmental driver of night-time NEE. The forest experienced unusual above-average annual rainfall during the first 2 years of this 3-year period so that soil water content remained relatively high and the forest was not water limited. Our results show the potential of temperate eucalypt forests to sequester large amounts of carbon when not water limited. However, further studies using bottom-up approaches are needed to validate measurements from the eddy covariance flux tower and to account for a possible underestimation in ER due to advection fluxes.

Oxygen Depletion and Winterkill Risk in Small Prairie Lakes Under Extended Ice Cover

1979 ◽  
Vol 36 (8) ◽  
pp. 980-986 ◽  
Author(s):  
Jan Barica ◽  
John A. Mathias
Keyword(s):  
Dissolved Oxygen ◽  
Average Rate ◽  
Oxygen Depletion ◽  
Oxygen Storage ◽  
Lake Depth ◽  
Fish Kill ◽  
Initial Oxygen ◽  
Storage Rate ◽  
Prairie Lakes ◽  
The Mean

Mean rates of dissolved oxygen depletion in 10 shallow eutrophic prairie lakes (area 2.3–27.3 ha, mean depth 1.6–4.2 m), ranged from 0.22 to 0.34 g/m2∙d−1 for nonstratified lakes and 0.32–0.42 g/m2∙d−1 for stratified ones. An average rate for all lakes was 0.29 ± 0.06 g/m2∙d−1. The rates correlated with the lake depth. A method for estimating the winterkill risk on the basis of initial oxygen storage, rate of dissolved oxygen depletion and/or the mean or maximum lake depth is proposed. Key words: prairie lakes, oxygen depletion rates, winter fish kill, eutrophication, metabolism, oxygen storage

scholarly journals A correlation between protein thermostability and resistance to proteolysis

1982 ◽  
Vol 207 (3) ◽  
pp. 641-644 ◽  
Author(s):  
R M Daniel ◽  
D A Cowan ◽  
H W Morgan ◽  
M P Curran
Keyword(s):  
Thermal Stability ◽  
Thermal Instability ◽  
Soluble Proteins ◽  
Protein Thermostability ◽  
General Correlation ◽  
Similar Correlation ◽  
Different Temperatures ◽  
Micro Organisms ◽  
Different Sources ◽  
Beta Galactosidase

The loss of activity due to proteolysis of purified L-asparaginase and beta-galactosidase from different sources correlates with the thermal instability of the enzymes. A similar correlation is found when populations of soluble proteins from micro-organisms grown at different temperatures are compared for proteolytic susceptibility and thermal stability. It is proposed that there is a general correlation between the thermostability of proteins and their resistance to proteolysis.

Sign in / Sign up

Export Citation Format

Share Document