scholarly journals Breaking Free from Thermodynamic Constraints: Thermal Acclimation and Metabolic Compensation in a freshwater zooplankton species

2020 ◽  
pp. jeb.237727
Author(s):  
B. L. Coggins ◽  
C. E. Anderson ◽  
R. Hasan ◽  
A. C. Pearson ◽  
M. N. Ekwudo ◽  
...  
Keyword(s):  
Heat Tolerance ◽  
Structural Changes ◽  
Temperature Response ◽  
Irreversible Damage ◽  
Freshwater Zooplankton ◽  
Respiration Rates ◽  
Metabolic Compensation ◽  
Filtering Rate ◽  
Higher Temperature ◽  
Environmental Temperatures

Ectothermic organisms’ respiration rates are affected by environmental temperatures, and sustainable metabolism at high temperatures sometimes limits heat tolerance. Organisms are hypothesized to exhibit acclimatory metabolic compensation effects, decelerating their metabolic processes below Arrhenius expectations based on temperature alone. We tested the hypothesis that either heritable or plastic heat tolerance differences can be explained by metabolic compensation in the eurythermal freshwater zooplankton crustacean Daphnia magna. We measured respiration rates in a ramp-up experiment over a range of assay temperatures (5 °C - 37 °C) in 8 genotypes of Daphnia representing a range of previously reported acute heat tolerances and, in a narrower range of temperatures (10 °C - 35 °C), in Daphnia with different acclimation history (either 10°C or 25°C). We discovered no difference in temperature-specific respiration rates between heat tolerant and heat-sensitive genotypes. In contrast, we observed acclimation-specific compensatory differences in respiration rates at both extremes of the temperature range studied. Notably, there was a deceleration of oxygen consumption at higher temperature in the 25°C-acclimated Daphnia relative to their 10°C-acclimated counterparts, observed in active animals, a pattern corroborated by similar changes in filtering rate and, partly, by changes in mitochondrial membrane potential. A recovery experiment indicated that the reduction of respiration was not caused by irreversible damage during exposure to a sublethal temperature. Response time necessary to acquire the respiratory adjustment to high temperature was lower than to low temperature, indicating that metabolic compensation at the lower temperatures require slower, possibly structural changes.

The effects of environmental temperature and method of feeding on the performance and carcass composition of bacon pigs

1967 ◽  
Vol 9 (2) ◽  
pp. 209-218 ◽  
Author(s):  
D. W. Holme ◽  
W. E. Coey
Keyword(s):  
Environmental Temperature ◽  
Average Daily Gain ◽  
Carcass Composition ◽  
Restricted Feeding ◽  
Feed Conversion ◽  
Feeding Method ◽  
Feeding Regimes ◽  
Higher Temperature ◽  
Ad Libitum ◽  
Environmental Temperatures

A trial designed to investigate the effects of two environmental temperatures, three feeding regimes and the interactions between them is described. A temperature of 72° F. was better than one of 54° F. for bacon pigs between 40 lb. and 200 lb. weight. The higher temperature resulted in faster growth, more efficient feed conversion and increased length of carcass. Other carcass characteristics were not significantly altered. Ad libitum feeding resulted in faster growth and fatter carcasses than restricted feeding, but did not have a significant effect on efficiency of feed conversion. When feed intake was restricted, feeding pigs once daily or twice daily resulted in similar performance and carcass composition.There was a significant interaction between environmental temperature and feeding method for average daily gain in that pigs fed ad libitum grew faster at the low temperature and pigs fed restricted amounts of feed grew faster at the high temperature. No other interaction reached significant levels.

Structural changes from polyimide films to graphite: Part IV. Novax and PPT

1995 ◽  
Vol 10 (4) ◽  
pp. 1024-1027 ◽  
Author(s):  
C. Bourgerette ◽  
A. Oberlin ◽  
M. Inagaki
Keyword(s):  
Long Range ◽  
Structural Changes ◽  
Film Plane ◽  
High Rank ◽  
Polyimide Films ◽  
Electron Microscopies ◽  
Higher Temperature ◽  
Cross Linker ◽  
Graphite Part

Various polyimide films (Kapton, Upilex, Novax, and PPT) were carbonized and graphitized up to 3000 °C. They were studied by optical and electron microscopies. All films retaining oxygen as a cross linker over 1000 °C, i.e., Kapton, Upilex, and Novax, graphitize as anthracites (high rank coals) do. They get a long range statistical orientation parallel to the film plane with a nanotexture of flattened pores. Graphitization is both sudden and perfect above 2100 °C when the pore walls break. Since oxygen is released at 1000 °C, the film PPT behaves as a compact nonporous graphitizing carbon (orientation parallel to the film plane). Thermal graphitization is progressive and begins at a higher temperature.

scholarly journals Metabolic tradeoffs and heterogeneity in microbial responses to temperature determine the fate of litter carbon in simulations of a warmer world

2019 ◽  
Vol 16 (24) ◽  
pp. 4875-4888
Author(s):  
Grace Pold ◽  
Seeta A. Sistla ◽  
Kristen M. DeAngelis
Keyword(s):  
Empirical Studies ◽  
Temperature Response ◽  
Extracellular Enzyme ◽  
Soil C ◽  
C Cycle ◽  
C Stocks ◽  
Microbial Responses ◽  
Higher Temperature ◽  
Projected Changes ◽  
Response To Temperature

Abstract. Climate change has the potential to destabilize the Earth's massive terrestrial carbon (C) stocks, but the degree to which models project this destabilization to occur depends on the kinds and complexities of microbial processes they simulate. Of particular note is carbon use efficiency (CUE), which determines the fraction of C processed by microbes that is anabolized into microbial biomass rather than lost to the atmosphere and soil as carbon dioxide and extracellular products. The temperature sensitivity of CUE is often modeled as an intrinsically fixed (homogeneous) property of the community, which contrasts with empirical data and has unknown impacts on projected changes to the soil C cycle under global warming. We used the Decomposition Model of Enzymatic Traits (DEMENT) – which simulates taxon-level litter decomposition dynamics – to explore the effects of introducing organism-level heterogeneity into the CUE response to temperature for decomposition of leaf litter under 5 ∘C of warming. We found that allowing the CUE temperature response to differ between taxa facilitated increased loss of litter C, unless fungal taxa were specifically restricted to decreasing CUE with temperature. Litter C loss was exacerbated by variable and elevated CUE at higher temperature, which effectively lowered costs for extracellular enzyme production. Together these results implicate a role for diversity of taxon-level CUE responses in driving the fate of litter C in a warmer world within DEMENT, which should be explored within the framework of additional model structures and validated with empirical studies.

scholarly journals Influence of Erbium Doping on Dielectric Properties of Zinc Borotellurite Glass System

2016 ◽  
Vol 846 ◽  
pp. 161-171 ◽  
Author(s):  
Siti Shafinas Zulkefly ◽  
Halimah Mohamed Kamari ◽  
Muhammad Nor Azlan Abdul Azis ◽  
Wan Mohd Daud Wan Yusoff
Keyword(s):  
Dielectric Properties ◽  
Molar Volume ◽  
Structural Changes ◽  
Low Frequency ◽  
Interfacial Polarization ◽  
Xrd Analysis ◽  
Glass System ◽  
Response Measurement ◽  
Xrd Pattern ◽  
Higher Temperature

Glasses of the system {[ (TeO2)70 (B2O3)30]70 (ZnO)30}100-y (Er2O3)y containing different concentration of Er2O3 (ranging from 0 to 5 mol %) was prepared from melt-quenching technique. The structural changes were studied by XRD analysis and FTIR analysis. The XRD pattern shows the glasses are amorphous. The higher concentration of Er2O3, the more unit of TeO3 would transform to TeO4 and formation of B-O vibrational groups. The density and molar volume was obtained attribute to non-bridging oxygen (NBO) and are found the density and molar volume of the glass system are increasing. The densities range from 3630 kg/m3 to 3960 kg/m3. The dielectric constant ε’ and dielectric loss factor ε’’ which were characterized in the frequency range 10-2 – 106 Hz over temperature range 50°C – 200 °C, show a larger value at lower frequency and higher temperature (above 110°C ). The results of dielectric response measurement show that interfacial polarization at low frequency, and orientation polarization at intermediate and high frequency.Keywords: Dielectric properties; Activation Energy; Rare Earth; Polarization; Non-Bridging Oxygen;

Multiple dielectric anomalies in xBiLaO3–(1 − x)PbTiO3 piezoelectrics

2008 ◽  
Vol 23 (2) ◽  
pp. 565-569 ◽  
Author(s):  
Runrun Duan ◽  
Michael S. Haluska ◽  
Robert F. Speyer
Keyword(s):  
Differential Scanning Calorimetry ◽  
Dielectric Constant ◽  
Excellent Agreement ◽  
Structural Changes ◽  
Dielectric Anomaly ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Thermally Induced ◽  
X Ray ◽  
Higher Temperature

Compositions of xBiLaO3–(1 − x) PbTiO3 over the range 0 ≤ x ≤ 0.225 were calcined and sintered. The dielectric constant with temperature and differential scanning calorimetry measurements were in excellent agreement with respect to Curie-like tetragonal to cubic transformations starting at 495 °C for pure PbTiO3, shifting to lower temperatures with increasing x. For compositions of x ≥ 0.05, a second higher-temperature (∼600 °C) endotherm, and matching dielectric anomaly, were consistently observed, for which there were no structural changes indicated by hot-stage x-ray diffraction. This transformation was speculated to be based on a thermally induced desegregation of B-site cations.

Fabrication and properties of PVDF/expanded graphite nanocomposites

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Yuchao Li ◽  
R. K. Y. Li ◽  
S. C. Tjong
Keyword(s):  
Dielectric Constant ◽  
Percolation Threshold ◽  
Structural Changes ◽  
Vinylidene Fluoride ◽  
Expanded Graphite ◽  
Nucleating Agent ◽  
X Ray Diffraction ◽  
Melt Mixing ◽  
Poly Vinylidene Fluoride ◽  
Higher Temperature

AbstractPoly(vinylidene fluoride) (PVDF) nanocomposites filled with various expanded graphite (EG) contents were prepared via melt-mixing followed by hotpressing. The structure, electrical, and thermal properties of resulting nanocomposites were investigated. X-ray diffraction results indicated that the EG additions do not lead to structural changes of PVDF. Differential thermal calorimetry measurements revealed that EG act as a nucleating agent for PVDF molecular chains. The crystallization temperature shifted to higher temperature with increasing EG content. DMA results showed that the storage modulus and glass transition temperature can be enhanced by adding EG. The nanocomposites were found to exhibit a small percolation threshold of 6.3 vol% due to the large aspect ratio of graphite nano-sheets. A great enhancement of dielectric constant is also found as EG concentration approaches percolation threshold. Both the electrical conductivity and dielectric constant of PVDF/EG nanocomposites can be well described by the percolation theory.

scholarly journals Juvenile Heat Tolerance in Wheat for Attaining Higher Grain Yield by Shifting to Early Sowing in October in South Asia

Genes ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1808
Author(s):  
Uttam Kumar ◽  
Ravi Prakash Singh ◽  
Susanne Dreisigacker ◽  
Marion S. Röder ◽  
Jose Crossa ◽  
...  
Keyword(s):  
Grain Yield ◽  
Heat Tolerance ◽  
Agronomic Traits ◽  
Central India ◽  
New Delhi ◽  
Crop Season ◽  
Wheat Varieties ◽  
Terminal Heat Stress ◽  
Available Soil Moisture ◽  
Higher Temperature

Farmers in northwestern and central India have been exploring to sow their wheat much earlier (October) than normal (November) to sustain productivity by escaping terminal heat stress and to utilize the available soil moisture after the harvesting of rice crop. However, current popular varieties are poorly adapted to early sowing due to the exposure of juvenile plants to the warmer temperatures in the month of October and early November. Therefore, a study was undertaken to identify wheat genotypes suited to October sowing under warmer temperatures in India. A diverse collection of 3322 bread wheat varieties and elite lines was prepared in CIMMYT, Mexico, and planted in the 3rd week of October during the crop season 2012–2013 in six locations (Ludhiana, Karnal, New Delhi, Indore, Pune and Dharwad) spread over northwestern plains zone (NWPZ) and central and Peninsular zone (CZ and PZ; designated as CPZ) of India. Agronomic traits data from the seedling stage to maturity were recorded. Results indicated substantial diversity for yield and yield-associated traits, with some lines showing indications of higher yields under October sowing. Based on agronomic performance and disease resistance, the top 48 lines (and two local checks) were identified and planted in the next crop season (2013–2014) in a replicated trial in all six locations under October sowing (third week). High yielding lines that could tolerate higher temperature in October sowing were identified for both zones; however, performance for grain yield was more promising in the NWPZ. Hence, a new trial of 30 lines was planted only in NWPZ under October sowing. Lines showing significantly superior yield over the best check and the most popular cultivars in the zone were identified. The study suggested that agronomically superior wheat varieties with early heat tolerance can be obtained that can provide yield up to 8 t/ha by planting in the third to fourth week of October.

scholarly journals GAS EXCHANGE CHARACTERISTICS OF FIELD-GROWN `SHAWNEE' BLACKBERRY

HortScience ◽  
1991 ◽  
Vol 26 (6) ◽  
pp. 687G-688
Author(s):  
Curt R. Rom ◽  
John R. Clark
Keyword(s):  
Gas Exchange ◽  
Dark Respiration ◽  
Temperature Response ◽  
Quadratic Function ◽  
Respiration Rates ◽  
Leaf Chamber ◽  
Portable System ◽  
Use Efficiency ◽  
Gas Exchange Characteristics ◽  
Chamber Gas

Gas exchange (assimilation, transpiration, water use efficiency, and conductance) of `Shawnee' blackberry were measured under field conditions with a portable system (ADC-IRGA with Parkinson Leaf Chamber). Gas exchange primocane pentifoliate leaflets were similar. Gas exchange rates of leaves along a cane exhibited a quadratic function of leaf position with leaves in lower-mid sections (relative position 0.3 - 0.5) having higher A, TR, WUE, gs than either basal or apical leaves. Leaves subtending fruiting laterals on fruiticanes had higher assimilation than similar age leaves on primocanes but did not differ in Tr, WUE, or gs. Primocanes had estimated dark respiration rates of 0.33mg·dm-1.hr-1, estimated light compensation at 14-20 mol.m-2.s-1, estimated light saturation at 1000-1100 mol.m-2.s-1 with maximum A rates ranging from 24-30 mg CO2.dm-1.hr-1. Measurements were made at field temperatures ranging from 24-35 C. Although temperature response was not measured, correlation indicated that Tr, WUE, and gs were more closely related to temperature than A. Similarly, Tr and WUE were more closely related to gs than A (r = 0.6 to 0.8).

scholarly journals Leaf heat tolerance of 147 tropical forest species varies with elevation and leaf functional traits, but not with phylogeny

2020 ◽  
Author(s):  
Martijn Slot ◽  
Daniela Cala ◽  
Jorge Aranda ◽  
Aurelio Virgo ◽  
Sean Michaletz ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Heat Tolerance ◽  
Phylogenetic Signal ◽  
Interspecific Variation ◽  
Leaf Mass Per Area ◽  
Mean Annual Temperature ◽  
Forest Species ◽  
Irreversible Damage ◽  
Photosystem Ii Efficiency ◽  
Thermal Thresholds

Exceeding thermal thresholds causes irreversible damage and ultimately loss of leaves. The lowland tropics are among the warmest forested biomes, but little is known about heat tolerance of tropical forest species. We surveyed leaf heat tolerance of sun-exposed leaves from 147 tropical lowland and pre-montane forest species by determining the temperatures at which potential photosystem II efficiency based on chlorophyll a fluorescence started to decrease (T) and had decreased by 50% (T). T averaged 46.7°C (5–95 percentile: 43.5–49.7°C) and T averaged 49.9°C (47.8–52.5°C). Heat tolerance partially adjusted to site temperature; T and T decreased with elevation by 0.40°C and 0.26°C per 100m, respectively, while mean annual temperature decreased by 0.63°C per 100m. The phylogenetic signal in heat tolerance was weak, suggesting that heat tolerance is more strongly controlled by environment than by evolutionary legacies. T increased with the estimated thermal time constant of the leaves, indicating that species with thermally buffered leaves maintain higher heat tolerance. Among lowland species, T increased with leaf mass per area, so species with structurally more costly leaves reduce the risk of leaf loss during hot spells. These results provide insight in interspecific variation in heat tolerance at local and regional scales.

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