scholarly journals The relationship between silicon isotope fractionation in sponges and silicic acid concentration: Modern and core-top studies of biogenic opal

2012 ◽  
Vol 81 ◽  
pp. 1-12 ◽  
Author(s):  
Katharine R. Hendry ◽  
Laura F. Robinson
Keyword(s):  
Acid Concentration ◽  
Silicic Acid ◽  
Isotope Fractionation ◽  
Silicon Isotope ◽  
Biogenic Opal ◽  
The Relationship

scholarly journals Silicon isotope fractionation and uptake dynamics of three crop plants: laboratory studies with transient silicon concentrations

2020 ◽  
Author(s):  
Daniel A. Frick ◽  
Rainer Remus ◽  
Michael Sommer ◽  
Jürgen Augustin ◽  
Friedhelm von Blanckenburg
Keyword(s):  
Stable Isotope ◽  
Plant Growth ◽  
Diffusion Process ◽  
Silicic Acid ◽  
Isotope Fractionation ◽  
Crop Plants ◽  
Transfer Efficiency ◽  
Silicon Isotope ◽  
Fractionation Factor ◽  
Stable Isotope Fractionation

Abstract. Silicon has been recognized an important element in global biogeochemical cycles for a long time. Recently, its relevance for global crop production gains increasing attention. Silicon is beneficial for plant growth and is taken up in considerable amounts by crops, likewise rice or wheat. The incorporation of silicic acid from the soil solution into the plants is accomplished by a variety of strategies (rejective, passive and active) that are subject to an intense debate. To forge a new perspective on the underlying processes, we investigated how the silicon stable isotope fractionation during plant growth depends on uptake strategy, transpiration, water use, and Si transfer efficiency. Crop plants with a rejective (tomato, Solanum lycopersicum and mustard, Sinapis alba) and active (spring wheat, Triticum aestivum) uptake were hydroponically grown for 6 weeks. Using inductively coupled plasma mass spectrometry, the silicon amounts and the isotopic composition of the nutrient solution, the roots, and the shoots were determined. Wheat revealed the highest Si transfer efficiency from root to shoot followed by tomato and mustard. All three species preferentially incorporated light 28Si, with a fractionation factor 1000∙ln(α) of −0.33 ‰ (tomato), −0.55 ‰ (mustard) and −0.43 ‰ (wheat). Even though the rates of active and passive Si root uptake differ, the physico-chemical processes governing Si uptake and stable isotope fractionation do not, they are governed by a diffusion process. In contrast, the transport of silicic acid from the roots to the shoots depends on the preceding precipitation of silicic acid in the roots and the presence of active transporters at the root endodermis. Plants with a significant biogenic silica precipitation in roots (mustard, and wheat), preferentially transport silicon enriched in 30Si into their shoots, whereas the transport in tomato is governed by a diffusion process and hence preferentially transports light silicon 28Si into the shoots.

Temperature and its measurement

2017 ◽  
Author(s):  
Andrew Clarke
Keyword(s):  
Thermal Equilibrium ◽  
Isotope Fractionation ◽  
Thermodynamic Temperature ◽  
The Other ◽  
Deterministic Models ◽  
Triple Point Of Water ◽  
Temperature Scales ◽  
Classical Thermodynamics ◽  
The Relationship ◽  
Unit Of Temperature

Temperature is that property of a body which determines whether it gains or loses energy in a particular environment. In classical thermodynamics temperature is defined by the relationship between energy and entropy. Temperature can be defined only for a body that is in thermodynamic and thermal equilibrium; whilst organisms do not conform to these criteria, the errors in assuming that they do are generally small. The Celsius and Fahrenheit temperature scales are arbitrary because they require two fixed points, one to define the zero and the other to set the scale. The thermodynamic (absolute) scale of temperature has a natural zero (absolute zero) and is defined by the triple point of water. Its unit of temperature is the Kelvin. The Celsius scale is convenient for much ecological and physiological work, but where temperature is included in statistical or deterministic models, only thermodynamic temperature should be used. Past temperatures can only be reconstructed with the use of proxies, the most important of which are based on isotope fractionation.

The relationship between the cobalt nutrition of ewes and the vitamin B12 status of ewes and their lambs

1987 ◽  
Vol 38 (6) ◽  
pp. 1071 ◽  
Author(s):  
MF Quirk ◽  
BW Norton
Keyword(s):  
Vitamin B12 ◽  
Milk Production ◽  
Acid Concentration ◽  
Methylmalonic Acid ◽  
Vitamin B12 Deficiency ◽  
Lactation Performance ◽  
Lower Productivity ◽  
Cotton South ◽  
B12 Deficiency ◽  
The Relationship

An experiment was undertaken at Mt Cotton, south-east Queensland, to investigate the relationship between the cobalt nutrition of ewes and the occurrence of vitamin B12 deficiency in ewes and their lambs. Ewes received either no supplementary cobalt (C), 0.03 mg cobalt day-1 (LC), 0.06 mg cobalt day-1 (HC) or a cobalt bullet and grinder (CB). LC and HC ewes received their supplement as a weekly drench. Supplementation commenced prior to joining, and ewes subsequently grazed pangola grass pastures containing between 0.05 and 0.11 mg kg-1 cobalt.Cobalt supplementation of ewes increased their liveweight, reproductive and lactation performance. The milk production of ewes was influenced by the level of supplementation, with C, LC, HC and CB ewes producing 31.1, 41.5, 47.7 and 50.31. of milk respectively during the first 4 weeks of lactation. The lower productivity of C ewes was associated with concentrations of vitamin B12 in serum of less than 200 pg ml-1 and with the presence of detectable concentrations of methylmalonic acid (>80 8moles l-1) and formiminoglutamic acid (>30 8moles l-1) in their urine.The growth of lambs was influenced by the cobalt nutrition of their dams; the mean liveweight gain from birth to weaning (14 weeks of age) for lambs from C, LC, HC and CB ewes was 95, 158, 194 and 231 g day-1. Vitamin B12 deficiency was evident in lambs reared by C ewes from 4 weeks of age, but lambs from LC and HC ewes did not become deficient until 8 and 12 weeks of age respectively. Lambs from CB ewes remained free of signs of deficiency prior to weaning. Urinary formiminoglutamic acid concentration was a more reliable indicator of vitamin B12 status in young lambs than urinary methylmalonic acid concentration. The concentrations of vitamin B12 in the serum of lambs were low in all groups (< 150 pg ml-1) and were generally unaffected by the cobalt nutrition of their dams.A dietary cobalt intake of about 0.15 mg day-1 appeared to be necessary for optimal milk production from ewes. However, this level of dietary cobalt was inadequate for provision of sufficient quantities of maternal vitamin B12 to meet the requirements of lambs in the later stages of lactation.

Enhancement of Borosilicate Glass Dissolution by Silica Sorption and Diffusion in Compacted Bentonite: A Model Study.

1990 ◽  
Vol 212 ◽  
Author(s):  
Enzo Curti ◽  
P. A. Smith
Keyword(s):  
Corrosion Rate ◽  
Acid Concentration ◽  
Silicic Acid ◽  
Computer Code ◽  
Glass Block ◽  
Concentration Gradients ◽  
Compacted Bentonite ◽  
Glass Corrosion ◽  
Model Study ◽  
Average Corrosion Rate

ABSTRACTExperimental evidence indicates that glass corrosion rates decrease proportionally with the increase of silicic acid concentration in the solution contacting the glass surface. A minimum corrosion rate (Rsat) is reached when the solution becomes saturated with respect to an unidentified amorphous siliceous compound. In a repository where the vitrified waste form is surrounded by compacted bentonite, the silica dissolved from the glass will diffuse into the pore solution and concentration gradients will be established throughout the backfill material. The silicic acid concentration at the glass-bentonite interface, and thus the glass corrosion rate, will then be diffusion controlled. Moreover, experimental work suggests that significant sorption of silica by clay minerals in bentonite may accelerate glass corrosion.A model describing glass corrosion coupled with diffusive transport and sorption of silica in bentonite has been developed and incorporated in a FORTRAN computer code (GLADIS). The model assumes: (a) a linear isotherm for the sorption of silica (KD), (b) time and space invariant pH, temperature and ionic strength, (c) proportionality between the quantity of silica precipitated and the amount of glass dissolved and (d) cylindrical geometry. Preliminary calculations with a particular parameter set at 90°C, assuming no silica sorption on the bentonite, indicate for an unfractured glass block that a stationary state is rapidly reached in which the silica concentration at the glass-bentonite interface is lower than the saturation concentration. This implies that the glass corrodes at a more rapid rate than Rsat (RsS ∼ 8 Rsat) If moderate silica sorption is assumed (KD = 0.5 m3 kg−1), the attainment of stationary conditions is delayed by the removal of silicic acid from solution, and the average corrosion rate is further increased by a factor ∼ 2.

scholarly journals Contribution of changes in opal productivity and nutrient distribution in the coastal upwelling systems to Late Pliocene/Early Pleistocene climate cooling

2012 ◽  
Vol 8 (5) ◽  
pp. 1435-1445 ◽  
Author(s):  
J. Etourneau ◽  
C. Ehlert ◽  
M. Frank ◽  
P. Martinez ◽  
R. Schneider
Keyword(s):  
Southern Ocean ◽  
Coastal Upwelling ◽  
Atmospheric Co2 ◽  
Early Pleistocene ◽  
Silicon Isotope ◽  
Time Interval ◽  
Nutrient Distribution ◽  
Biogenic Opal ◽  
Late Pliocene ◽  
Polar Ocean

Abstract. The global Late Pliocene/Early Pleistocene cooling (~3.0–2.0 million years ago – Ma) concurred with extremely high diatom and biogenic opal production in most of the major coastal upwelling regions. This phenomenon was particularly pronounced in the Benguela upwelling system (BUS), off Namibia, where it is known as the Matuyama Diatom Maximum (MDM). Our study focuses on a new diatom silicon isotope (δ30Si) record covering the MDM in the BUS. Unexpectedly, the variations in δ30Si signal follow biogenic opal content, whereby the highest δ30Si values correspond to the highest biogenic opal content. We interpret the higher δ30Si values during the MDM as a result of a stronger degree of silicate utilisation in the surface waters caused by high productivity of mat-forming diatom species. This was most likely promoted by weak upwelling intensity dominating the BUS during the Late Pliocene/Early Pleistocene cooling combined with a large silicate supply derived from a strong Southern Ocean nutrient leakage responding to the expansion of Antarctic ice cover and the resulting stratification of the polar ocean 3.0–2.7 Ma ago. A similar scenario is hypothesized for other major coastal upwelling systems (e.g. off California) during this time interval, suggesting that the efficiency of the biological carbon pump was probably sufficiently enhanced in these regions during the MDM to have significantly increased the transport of atmospheric CO2 to the deep ocean. In addition, the coeval extension of the area of surface water stratification in both the Southern Ocean and the North Pacific, which decreased CO2 release to the atmosphere, led to further enhanced atmospheric CO2 drawn-down and thus contributed significantly to Late Pliocene/Early Pleistocene cooling.

scholarly journals Prevalence of Hyperuricemia and the Relationship Between Serum Uric Acid Concentrations and Lipid Parameters Among King Abdulaziz University Hospital Patients

2021 ◽  
Author(s):  
Ranya A. Ghamri ◽  
Tala A. Qalai ◽  
Raghad A. Ismail ◽  
Joud M. Aljehani ◽  
Dina S. Alotaibi ◽  
...  
Keyword(s):  
Uric Acid ◽  
Lipid Profile ◽  
Serum Uric Acid ◽  
Acid Concentration ◽  
Density Lipoprotein ◽  
University Hospital ◽  
Uric Acid Concentration ◽  
Serum Uric Acid Concentration ◽  
King Abdulaziz University ◽  
The Relationship

Abstract Background: Hyperuricemia is a metabolic defect caused by high purine consumption, overproduction of uric acid, or reduced uric acid excretion. Hyperuricemia is the second most common metabolic disease after diabetes mellitus and can mediate proinflammatory endocrine imbalance in adipose tissue, which contributed to dyslipidemia. Furthermore, several studies have associated uric acid with dyslipidemia. However, no previous studies have examined patients without chronic illness. Thus, we aimed to assess the relationship between serum uric acid concentration and lipid profile parameters and to estimate the prevalence of hyperuricemia in the city of Jeddah. Methods: A retrospective study was conducted among 1206 patients without chronic illness after applying the exclusion criteria. Patients had undergone laboratory blood testing over a 3-year period (2018–2020) at King Abdulaziz University Hospital, which was ethically approved. We used a predesigned checklist to collect data from electronic hospital records using Google Forms. Bivariate analysis, tables, and graphs were used to represent and identify the relationships between variables. A P-value of <0.05 was considered significant.Results: Our study revealed a prevalence of 12% for hyperuricemia in the study population. Males were more frequently affected than females (8.13% vs. 3.73%, respectively). There was no association between serum uric acid concentration and lipid profile parameters, including total cholesterol (P = 0.92), triglyceride (P = 0.42), high-density lipoprotein (P = 0.47), and low-density lipoprotein (P = 0.66). There was a strong association between serum uric acid concentration and high body mass index (P < 0.001), older age (P = 0.002), male sex (P < 0.001), and nationality (P < 0.001). Furthermore, there was an association between sex and mean erythrocyte sedimentation rate (P = 0.02) and mean triglyceride concentration (P = 0.02).Conclusion: We observed a low prevalence of hyperuricemia, and our results indicate no association between serum uric acid concentration and lipid profile parameters.

scholarly journals Inverse association between coffee drinking and serum uric acid concentrations in middle-aged Japanese males

1999 ◽  
Vol 82 (2) ◽  
pp. 125-130 ◽  
Author(s):  
C. Kiyohara ◽  
S. Kono ◽  
S. Honjo ◽  
I. Todoroki ◽  
Y. Sakurai ◽  
...  
Keyword(s):  
Uric Acid ◽  
Serum Uric Acid ◽  
Green Tea ◽  
Acid Concentration ◽  
Coffee Consumption ◽  
Uric Acid Concentration ◽  
Coffee Drinking ◽  
Serum Uric Acid Concentration ◽  
The Relationship ◽  
Self Defence

Consumption of caffeine-rich beverages, which have diuretic properties, may decrease serum uric acid concentrations. We examined cross-sectionally the relationship of coffee and green tea consumption to serum uric acid concentrations in 2240 male self-defence officials who received a pre-retirement health examination at four hospitals of the Self-Defence Forces between 1993 and 1994. The mean levels of coffee and green tea consumption were 2·3 and 3·1 cups/d respectively. There was a clear inverse relationship between coffee consumption and serum uric acid concentration. When adjusted for hospital only, those consuming less than one cup of coffee daily had a mean serum uric acid concentration of 60 mg/l, while that of those drinking five or more cups of coffee daily was 56 mg/l (P < 0·0001). No such relationship was observed for green tea, another major dietary source of caffeine in Japan. The relationship between coffee consumption and serum uric acid concentration was independent of age, rank in the Self-Defence Forces, BMI, systolic blood pressure, serum creatinine, serum total cholesterol and serum HDL-cholesterol concentrations, smoking status, alcohol use, beer consumption and intake of dairy products. These findings suggest that coffee drinking may be associated with lower concentrations of serum uric acid, and further studies are needed to confirm the association.

Sign in / Sign up

Export Citation Format

Share Document