Detection of widespread fluids in the Tibetan crust by magnetotelluric studies

Magnetotelluric exploration has shown that the middle and lower crust is anomalously conductive across most of the north-to-south width of the Tibetan plateau. The integrated conductivity (conductance) of the Tibetan crust ranges from 3000 to greater than 20,000 siemens. In contrast, stable continental regions typically exhibit conductances from 20 to 1000 siemens, averaging 100 siemens. Such pervasively high conductance suggests that partial melt and/or aqueous fluids are widespread within the Tibetan crust. In southern Tibet, the high-conductivity layer is at a depth of 15 to 20 kilometers and is probably due to partial melt and aqueous fluids in the crust. In northern Tibet, the conductive layer is at 30 to 40 kilometers and is due to partial melting. Zones of fluid may represent weaker areas that could accommodate deformation and lower crustal flow.     

Kimmswick: a clovis-mastodon association in eastern missouri

Stone tools characteristic of the Clovis culture have been found in direct association with bones of the American mastodon at Kimmswick, Missouri. The vertebrate fauna from Clovis components suggests a deciduous woodland and meadow habitat. Such an environmental reconstruction provides a new perspective for Clovis adaptations and the ecological tolerances of Mammut americanum.     

Four-dimensional heteronuclear triple-resonance NMR spectroscopy of interleukin-1 beta in solution

A method is presented that dramatically improves the resolution of protein nuclear magnetic resonance (NMR) spectra by increasing their dimensionality to four. The power of this technique is demonstrated by the application of four-dimensional carbon-13--nitrogen-15 (13C-15N)--edited nuclear Overhauser effect (NOE) spectroscopy to interleukin-1 beta, a protein of 153 residues. The NOEs between NH and aliphatic protons are first spread out into a third dimension by the 15N chemical shift of the amide 15N atom and subsequently into a fourth dimension by the 13C chemical shift of the directly bonded 13C atoms. By this means ambiguities in the assignment of NOEs between NH and aliphatic protons that are still present in the three-dimensional 15N-edited NOE spectrum due to extensive chemical shift overlap and degeneracy of aliphatic resonances are completely removed. Consequently, many more approximate interproton distance restraints can be obtained from the NOE data than was heretofore possible, thereby expanding the horizons of three-dimensional structure determination by NMR to larger proteins.     

Nutrient concentration relationships between the fourth petiole and upper-stem of potato plants

Successfully evaluating the nutritional status of a crop during growth and development is dependent upon sampling an identifiable plant part. Consistently sampling a petiole of the same maturity in potatoes (Solanum tuberosum L.) is difficult. We evaluated the nutrient relationships between the upper-stem and the fourth petiole from Russet Burbank plants in field studies having N, P, K, Zn or Mn variables. The upper-stem was obtained by excising the stem below the sixth leaf and removing all leaves and the terminal meristem. Petole NO₃-N, P, K, Zn and Mn concentrations were from deficient to sufficient. The NO₃-N, P and K concentrations were similar in the fourth petiole and upper-stem, while the Zn concentration was 40% higher in the upper-stem. Calcium, Mg and Mn concentrations were lower in the upper-stem than in the fourth petiole. Copper and S relationships were not adequately defined. The fourth petiole’s NO₃-N, P and K diagnostic concentrations now used to monitor plant nutrient status can also be used for upper-stem samples. Zinc diagnostic concentrations should be increased, while Ca, Mg and Mn concentrations should be adjusted downward in the upper-tem. Additional data are needed to refine the Ca and Mg relationships, and to establish relationships for Cu, S and other essential nutrients. A significant advantage of using the upper-stem is the elimination of the petiole selection problem when sampling.     

Variability in carbon sequestration potential in no-till soil landscapes of southern Ontario

Soil organic carbon (SOC) in Canadian agricultural soils plays an important role in the global cycle of C, and management can influence its fate. Although the scientific literature suggests that practicing no-till (NT) can sequester C, this is not always the case. Furthermore, there are many other factors including climate, management history, soil type and soil landscape processes that may affect the dynamics of SOC under NT. We measured the changes in SOC under NT in southern Ontario, at varying positions in the landscape in Gleyic and Orthic Luvisols at the end of a 15-year-period. Soil cores taken to depths beyond the solum, were segmented with depth, and total SOC was determined for each segment on an equivalent mass basis. When the entire soil column was considered, there was a loss of SOC in more profiles than there were gains. Furthermore, the erosion/deposition history at each landscape position appeared to influence the dynamics of SOC. In depression areas where A_p horizons were greater than 27 cm thick due to a history of soil deposition from upslope and local hydrology, there was a loss of total SOC after 15 years of NT. While where the A_p thickness was less than 27 cm, there were 18 profiles with SOC gains and 15 with net losses. Multiple linear regression analysis revealed that the change in SOC after 15 years was negatively related to the initial total SOC content and positively related to mass of clay. The results of this study suggest that landscape position and erosion/deposition history play a significant role in the ability of NT soils to sequester SOC. Interpretations of long-term SOC monitoring studies must take into account the location of samples within fields if useful information is to be gained on C dynamics in agricultural soils.     

Circulatory and blood gas changes accompanying the development and treatment of induced laminitis

A peripheral vasodilatory agent, isoxsuprine hydro-chloride, was evaluated in a controlled study for its efficacy in the treatment of acute equine laminitis. Eight healthy, adulthorses of variable age and sex were used in the trial. Acute laminitis was induced in 5 of the horses by oral carbohydrate overload. Intravenous isoxsuprine therapy (1.8 mg/kg) was initiated in 3 of the horses receiving carbohydrate overload at first sign of clinical lameness and repeated at 12-hour intervals. Intravenous saline placebos were administered on a similar schedule to 2 control horses which also received a carbohydrate overload. The remaining 3 horses served as further controls. Local and systemic responses to induction of laminitis and isoxsuprine administration were assessed by subjective evaluation of clinical lameness in a double blind trial; nuclear scintigraphy and radiography of the distal forelimbs; and assessment of physical, hematological and biochemical parameters.

Pronounced tachycardia, hypotension and sweating accompanied the intravenous infusion of isoxsuprine. The 3 horses treated with isoxsuprine following the induction of laminitis showed a more rapid improvement in soundness than horses receiving saline placebos. No horse developed rotation of the third phalanx in response to the diet Nuclear scintigraphy indicated that blood perfusion patterns within the hoof of laminitic horses altered with isoxsuprine therapy, but an overall increase or decrease in perfusion was not apparent. Alterations in serum enzyme and electrolyte profiles with the onset of laminitis generally concurred with findings previously reported for this model of the disease. No change in coagulation profiles accompanied the onset of laminitis or isoxsuprine administration. Blood gas analysis indicated an increase in median palmar vein oxygen partial pressure (PO₂) levels with onset of laminitis. A concurrent decrease in the median palmar arteriovenous oxygen partial pressure difference (AVO₂) was significant at the P<0.01 level. There was no difference in median palmar vein PO₂ values between thoseanimals receiving isoxsuprine and those receiving saline placebo therapy. Results of the trialindicated that isoxsuprine may be beneficial in the treatment of acute laminitis. Further controlled studies are appropriate.     

How does dietary particle size affect carnivore gastrointestinal transit: A dog model

The effect of dietary particle size on gastrointestinal transit in carnivores has not been studied and might offer more insight into their digestive physiology. This study evaluated the effect of two dietary particle sizes (fine = 7.8 mm vs. coarse = 13 mm) of chunked day‐old chicks on transit parameters in dogs. Six beagle dogs were fed both dietary treatments in a crossover design of 7 days with transit testing on the fifth day. Transit parameters were assessed using two markers, that is a wireless motility capsule (IntelliCap^®) and titanium oxide (TiO₂). Dietary particle size did not affect gastric emptying time (GRT), small bowel transit time (SBTT), colonic transit time (CTT) and total transit time (aTTT) of the capsule (p > .05). There was no effect of dietary particle size on TiO₂ mean retention time (MRT) (p > .05). The time of last TiO₂ excretion (MaxRT) differed (p = .013) between diets, being later for the coarse diet. Both MRT (R = 0.617, p = .032) and MaxRT (R = 0.814; p = .001) were positively correlated to aTTT. The ratio MRT/aTTT tended towards a difference between diets (p = .059) with the coarse diet exceeding fine diet values. Results show that the difference between capsule measurements and TiO₂ is larger for the fine than the coarse diet suggesting that the capsule becomes more accurate when dietary particle size approaches marker size. Dietary particle size might have affected transit parameters but differences are too small to claim major physiological consequences.     

Comparison of soil phosphorus extraction methods regarding their suitability for organic farming systems

Background

Organic farmers frequently report sufficient yield levels despite low or even very low soil phosphorous (P) contents questioning the applicability of widely used laboratory methods for soil P testing for organic farming.

Aims

The aim of this study was to compare the validity of a broad range of different soil extraction methods on soils under organic management from South West Germany and to test the correlation of the measured soil P concentration with plant offtake.

Methods

Twenty-two soil samples of eight different organic farms were extracted with different solutions: (1) water, (2) CAL, (3) Olsen, (4) Mehlich 3, (5) Bray P1, (6) Bray P2, (7) NaOH+Na₂EDTA, and (8) total P. The results were then correlated with above ground plant P.

Results

Spearman's rank correlation coefficient (r_s) of correlations between above ground plant P and extractable soil P (Water-P, CAL-P, and Olsen-P [+active charcoal {+AC}]) determined with ICP-OES were strong (0.94, 0.90, and 0.93, respectively). Among the tested methods, above ground plant P showed a strong correlation with CAL-P as detected by ICP-OES (r_s = 0.90) and colorimetry (r_s = 0.91). The comparison of CAL-P data provided by farmers and CAL-P analyzed during this research showed discrepancies between the results.

Conclusions

The results of this study indicate that the CAL method can be used in organic farming despite a low extraction of organic P (P_org). Furthermore, it is recommended for farmers to take soil samples for analyses regularly and interpret changes in P in the long-term instead of interpreting individual samples.