scholarly journals Gas exchange of captive freely diving grey seals (Halichoerus grypus).

1994 ◽  
Vol 191 (1) ◽  
pp. 1-18 ◽  
Author(s):  
J Z Reed ◽  
C Chambers ◽  
M A Fedak ◽  
P J Butler
Keyword(s):  
Gas Exchange ◽  
Oxygen Storage Capacity ◽  
Dive Duration ◽  
Minute Volume ◽  
Oxygen Storage ◽  
Allometric Relationships ◽  
Aerobic Dive Limit ◽  
Oxygen Utilisation ◽  
End Tidal ◽  
Limited Oxygen

When at sea, phocids dive for long periods and spend a high percentage of their time submerged. This behaviour requires some combination of an increased oxygen storage capacity, rapid oxygen loading at the surface and reduced oxygen utilisation when submerged. To assess these adaptations, breath-by-breath ventilation was studied in four adult grey seals (two male, two female, 160-250 kg), freely diving in a large outdoor tank where surface access was restricted to one breathing hole. The dive patterns obtained were similar to those recorded from freely diving wild grey seals. Respiratory frequency during the surface periods was 40% higher than that estimated from allometric relationships (19.4 +/- 0.7 breaths min-1), and tidal volume (6.3 +/- 1.21) was approximately five times higher than that estimated from allometric relationships. These adaptations produce a high minute volume and enable gas exchange to occur at the surface. Mean oxygen consumption rate (VO2, measured for a dive+surface cycle) decreased with increasing dive duration. The aerobic dive limit was estimated as 9.6 min for a 150 kg grey seal (using the overall average VO2 of 5.2 ml O2 min-1 kg-1), which is consistent with results from freely diving wild grey seals (only 6% of dives exceeded 10 min). End-tidal oxygen values varied during a surface period, following a U-shaped curve, which suggests that there is limited oxygen uptake from the lung and/or blood oxygen stores during dives. This result was unexpected and indicates that these seals are utilising substantial physiological responses to conserve oxygen, even during shallow voluntary diving.

Body oxygen stores, aerobic dive limits and diving behaviour of the star-nosed mole (Condylura cristata) and comparisons with non-aquatic talpids

2002 ◽  
Vol 205 (1) ◽  
pp. 45-54
Author(s):  
Ian W. McIntyre ◽  
Kevin L. Campbell ◽  
Robert A. MacArthur
Keyword(s):  
Skeletal Muscles ◽  
Storage Capacity ◽  
Metabolic Cost ◽  
Oxygen Storage Capacity ◽  
Dive Duration ◽  
Oxygen Storage ◽  
High Mass ◽  
The Mean ◽  
Total Body ◽  
Condylura Cristata

SUMMARY The dive performance, oxygen storage capacity and partitioning of body oxygen reserves of one of the world’s smallest mammalian divers, the star-nosed mole Condylura cristata, were investigated. On the basis of 722 voluntary dives recorded from 18 captive star-nosed moles, the mean dive duration (9.2±0.2 s; mean ± s.e.m.) and maximum recorded dive time (47 s) of this insectivore were comparable with those of several substantially larger semi-aquatic endotherms. Total body O2 stores of adult star-nosed moles (34.0 ml kg–1) were 16.4 % higher than for similarly sized, strictly fossorial coast moles Scapanus orarius (29.2 ml kg–1), with the greatest differences observed in lung and muscle O2 storage capacity. The mean lung volume of C. cristata (8.09 ml 100 g–1) was 1.81 times the predicted allometric value and exceeded that of coast moles by 65.4 % (P=0.0001). The overall mean myoglobin (Mb) concentration of skeletal muscles of adult star-nosed moles (13.57±0.40 mg g–1 wet tissue, N=7) was 19.5 % higher than for coast moles (11.36±0.34 mg g–1 wet tissue, N=10; P=0.0008) and 54.2 % higher than for American shrew-moles Neurotrichus gibbsii (8.8 mg g–1 wet tissue; N=2). The mean skeletal muscle Mb content of adult star-nosed moles was 91.1 % higher than for juveniles of this species (P<0.0001). On the basis of an average diving metabolic rate of 5.38±0.35 ml O2 g–1 h–1 (N=11), the calculated aerobic dive limit (ADL) of star-nosed moles was 22.8 s for adults and 20.7 s for juveniles. Only 2.9 % of voluntary dives by adult and juvenile star-nosed moles exceeded their respective calculated ADLs, suggesting that star-nosed moles rarely exploit anaerobic metabolism while diving, a conclusion supported by the low buffering capacity of their skeletal muscles. We suggest that a high mass-specific O2 storage capacity and relatively low metabolic cost of submergence are key contributors to the impressive dive performance of these diminutive insectivores.

scholarly journals Dive Performance and Aquatic Thermoregulation of the World’s Smallest Mammalian Diver, the American Water Shrew (Sorex palustris)

2021 ◽  
Author(s):  
Roman W. Gusztak ◽  
Robert A. MacArthur ◽  
Kevin L. Campbell
Keyword(s):  
Body Temperature ◽  
Core Body Temperature ◽  
Thermal Inertia ◽  
Oxygen Storage Capacity ◽  
Dive Duration ◽  
Oxygen Storage ◽  
Foraging Efficiency ◽  
Diving Behavior ◽  
In The Wild ◽  
Total Body Oxygen

AbstractAllometry predicts that the 12–17 g American water shrew (Sorex palustris)—the world’s smallest mammalian diver—will have the highest diving metabolic rate (DMR) coupled with the lowest total body oxygen storage capacity, skeletal muscle buffering capacity, and glycolytic potential of any endothermic diver. Despite these constraints, the maximum dive time (23.7 sec) and calculated aerobic dive limit (cADL; 10.8–14.4 sec) of wild-caught water shrews match or exceed values predicted by allometry based on studies of larger-bodied divers. The mean voluntary dive time of water shrews in 3, 10, 20, and 30°C water was 5.1±0.1 sec (N=25, n=1584), with a mean maximum dive time of 10.3±0.4 sec. Only 2.3–3.9% of dives in 30 and 10°C water, respectively, exceeded the cADL. Mean dive duration, duration of the longest dive, and total time in water all decreased significantly as temperature declined, suggesting that shrews employed behavioural thermoregulation to defend against immersion hypothermia. As expected from their low thermal inertia, diving shrews had a significantly higher DMR in 10°C (8.77 mL O2 g-1 hr-1) compared to 30°C water (6.57 mL O2 g-1 hr-1). Diving behavior of radio-telemetered shrews exclusively foraging in a simulated riparian environment (3°C water) for 12- to 28-hours suggest that mean (but not maximum) dive times of water shrews in the wild may be longer than predicted from our voluntary dive trials, as the average dive duration (6.9±0.2 sec, n=257) was ∼1.75× longer than during 20-min trials with no access to food at the same water temperature. Notably, free-diving shrews in the 24-hr trials consistently elevated core body temperature by ∼1.0–1.5°C immediately prior to initiating aquatic foraging bouts, and ended these bouts when body temperature was still at or above normal resting levels (∼37.8°C). We suggest this observed pre-dive hyperthermia aids to heighten the impressive somatosensory physiology, and hence foraging efficiency, of this diminutive predator while submerged.

scholarly journals First of Its Kind Automotive Catalyst Prepared by Recycled PGMs-Catalytic Performance

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 942
Author(s):  
Anastasia Maria Moschovi ◽  
Mattia Giuliano ◽  
Marios Kourtelesis ◽  
Giovanna Nicol ◽  
Ekaterini Polyzou ◽  
...  
Keyword(s):  
Oxygen Storage Capacity ◽  
Catalytic Performance ◽  
Platinum Group Metals ◽  
Oxygen Storage ◽  
Small Scale ◽  
Gas Mixture ◽  
Oxidation Reactions ◽  
Fresh Catalyst ◽  
Metal Precursors ◽  
Automotive Catalytic Converters

The production of new automotive catalytic converters requires the increase of the quantity of Platinum Group Metals in order to deal with the strict emission standards that are imposed for vehicles. The use of PGMs coming from the recycling of spent autocatalysts could greatly reduce the cost of catalyst production for the automotive industry. This paper presents the synthesis of novel automotive Three-Way Catalysts (PLTWC, Pd/Rh = 55/5, 60 gPGMs/ft3) and diesel oxidation catalysts (PLDOC, Pt/Pd = 3/1, 110 gPGMs/ft3) from recovered PGMs, without further refinement steps. The catalysts were characterized and evaluated in terms of activity in comparison with benchmark catalysts produced using commercial metal precursors. The small-scale catalytic monoliths were successfully synthesized as evidenced by the characterization of the samples with XRF analysis, optical microscopy, and N2 physisorption. Hydrothermal ageing of the catalysts was performed and led to a significant decrease of the specific surface area of all catalysts (recycled and benchmarks) due to sintering of the support material and metal particles. The TWCs were studied for their activity in CO and unburned hydrocarbon oxidation reactions under a slightly lean environment of the gas mixture (λ > 1) as well as for their ability to reduce NOx under a slightly rich gas mixture (λ < 1). Recycled TWC fresh catalyst presented the best performance amongst the catalysts studied for the abatement of all pollutant gases, and they also showed the highest Oxygen Storage Capacity value. Moreover, comparing the aged samples, the catalyst produced from recycled PGMs presented higher activity than the one synthesized with the use of commercial PGM metal precursors. The results obtained for the DOC catalysts showed that the aged PLDOC catalyst outperformed both the fresh catalyst and the aged DOC catalyst prepared with the use of commercial metal precursors for the oxidation of CO, hydrocarbons, and NO. The latter reveals the effect of the presence of several impurities in the recovered PGMs solutions.

Autothermal Reforming of Propane Over Ni Catalysts Supported on a Variety of Perovskites

2007 ◽  
Vol 7 (11) ◽  
pp. 4013-4016 ◽  
Author(s):  
SeungSoo Lim ◽  
DongJu Moon ◽  
JongHo Kim ◽  
YoungChul Kim ◽  
NamCook Park ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Storage Capacity ◽  
Flow Reactor ◽  
Oxygen Storage Capacity ◽  
Autothermal Reforming ◽  
Oxygen Storage ◽  
Hydrogen Yield ◽  
Impregnation Method ◽  
Ni Catalysts ◽  
Atmospheric Flow

Autothermal reforming of propane for hydrogen over Ni catalysts supported on a variety of perovskites was performed in an atmospheric flow reactor. Perovskite is known for its higher thermal stability and oxygen storage capacity, but catalytic activity of itself is low. A sites of the ABO3 structured perovskites were occupied by La while B sites by one of Fe, Co, Ni, and Al by citrate method. The composition of the reactant mixture was H2O/C/O2 = 8.96/1.0/1.1. The changes in the states of the catalysts after reaction were analyzed by XRD, TPD, and TGA. Ni/LaAlO3 catalyst maintained the perovskite structure after reaction. It showed higher hydrogen yield and thermal stability compared to those of the catalysts with Fe, Co, or Ni in B sites. Catalysts prepared by deposition-precipitation (DP) method showed higher activity than those prepared by impregnation method, presumably due to the smaller sizes of the NiO crystal particles.

Mn3O4 doped with highly dispersed Zr species: a new non-noble metal oxide with enhanced activity for three-way catalysis

2016 ◽  
Vol 40 (12) ◽  
pp. 10108-10115 ◽  
Author(s):  
Genyuan Zhao ◽  
Jing Li ◽  
Wenshuang Zhu ◽  
Xueqin Ma ◽  
Yonghua Guo ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Manganese Oxide ◽  
Noble Metal ◽  
Storage Capacity ◽  
Catalytic Properties ◽  
Oxygen Storage Capacity ◽  
Oxide Catalysts ◽  
Oxygen Storage ◽  
Highly Dispersed ◽  
Three Way Catalysis

Herein, we demonstrate the influence of zirconium species on promoting the oxygen storage capacity and three-way catalytic properties of zirconium-manganese oxide catalysts.

Oxygen Storage Capacity (OSC) Measurement of 3-Way Automotive Catalysts Using the CATAGEN OMEGA Test Reactor

2021 ◽  
Author(s):  
Liam Mc Grane ◽  
Roy Douglas ◽  
Kurtis Irwin ◽  
Andrew Woods ◽  
Jonathan Stewart ◽  
...  
Keyword(s):  
Storage Capacity ◽  
Oxygen Storage Capacity ◽  
Oxygen Storage ◽  
Automotive Catalysts ◽  
Test Reactor

Direct effect of PaCO2 on respiratory sinus arrhythmia in conscious humans

2002 ◽  
Vol 282 (3) ◽  
pp. H973-H976 ◽  
Author(s):  
Nobuko Sasano ◽  
Alex E. Vesely ◽  
Junichiro Hayano ◽  
Hiroshi Sasano ◽  
Ron Somogyi ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Direct Effect ◽  
Respiratory Sinus Arrhythmia ◽  
Random Order ◽  
Mean Amplitude ◽  
Frequency Component ◽  
Pulmonary Gas Exchange ◽  
High Frequency Component ◽  
Sinus Arrhythmia ◽  
End Tidal

Respiratory sinus arrhythmia (RSA) may improve the efficiency of pulmonary gas exchange by matching the pulmonary blood flow to lung volume during each respiratory cycle. If so, an increased demand for pulmonary gas exchange may enhance RSA magnitude. We therefore tested the hypothesis that CO2directly affects RSA in conscious humans even when changes in tidal volume (VT) and breathing frequency ( F B), which indirectly affect RSA, are prevented. In seven healthy subjects, we adjusted end-tidal Pco 2 (Pet CO2 ) to 30, 40, or 50 mmHg in random order at constant VT and F B. The mean amplitude of the high-frequency component of R-R interval variation was used as a quantitative assessment of RSA magnitude. RSA magnitude increased progressively with Pet CO2 ( P < 0.001). Mean R-R interval did not differ at Pet CO2 of 40 and 50 mmHg but was less at 30 mmHg ( P < 0.05). Because VT and F B were constant, these results support our hypothesis that increased CO2directly increases RSA magnitude, probably via a direct effect on medullary mechanisms generating RSA.

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