Age and timing of the Permian mass extinctions: U/Pb dating of closed-system zircons

The age and timing of the Permian-Triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive lead loss and contamination by indistinguishable older xenocrysts. Zircons from nine ash beds within the Shangsi and Meishan sections (China), pretreated by annealing followed by partial attack with hydrofluoric acid, result in suites of consistent and concordant uranium/lead (U/Pb) ages, eliminating the effects of lead loss. The U/Pb age of the main pulse of the extinction is 252.6 +/- 0.2 million years, synchronous with the Siberian flood volcanism, and it occurred within the quoted uncertainty.     

Grain quality characteristics of rice in Madagascar retail markets

A survey of rice in retail markets of Madagascar with emphasis on the surplus regions of Marovoay and Lac Alaotra and the deficient area, Antananarivo City showed rices of Madagascar to be predominantly medium-long, medium-shaped, with high apparent amylose content, low gelatinization temperature, and soft, hard or medium gel consistency. Mean protein content was 7.5%. Percent white grains among red and white grains ranged from 0 to 100% (mean 56%), head rice 0–94%, translucency 6–66% and Kett whiteness 12–48%.     

Long-term fertilization and plastic film mulching modify temporal incorporation of 13C/15N-labelled particulate organic matter

Plastic film mulching (PFM) is critical for agricultural planting and maximizing production in semiarid and arid areas. Particulate organic matter (POM) is assumed to be a sensitive indicator for evaluating the effects of different agricultural practices on soil fertility and the soil organic carbon (SOC) pool. Soil aggregates have the function of ‘wrap’ and protect the POM stored in them. However, there is limited information regarding how PFM and fertilization jointly influence the dynamic changes of newly added stalk-derived POM in brown earth. Consequently, an in-depth study of the fate of carbon (C) and nitrogen (N) derived from maize stalk residues within the particulate organic carbon (POC) and particulate organic nitrogen (PON) fractions in soil aggregates was undertaken. Its outcome would contribute to better predictions on the active organic matter components sequestered in the soil. The dynamics and accumulation of newly added maize stalk C and N as POC and PON in different soil aggregates (using the dry sieving method divided into >2, 1–2, 0.25–1 and <0.25 mm) were analysed by an in situ ¹³C/¹⁵N-tracing technique under PFM and different fertilization treatments. Over 360 days of cultivation, the POC and PON contents were significantly (p < 0.05) larger in the nitrogen (N) and organic manure (M) treatments than in the MN (manure combined with nitrogen) and Control treatments. The PFM treatment accelerated the decomposition of maize stalk C in the N fertilizer treatment, with an increase of 64% in stalk-derived POC after the 1-day cultivation period. Stalk-derived POM tended to accumulate in <0.25 mm microaggregates in the early cultivation period and then decreased rapidly with the extension of the cultivation period affected by PFM coupled with fertilization. However, stalk-derived POM accumulation in macroaggregates (>0.25 mm) fluctuated over the 360-day cultivation period. Accordingly, PFM application and fertilization practices had important effects on the accumulation of newly added stalk-derived POM in soil aggregates. We conclude that the accumulation of maize residue POM was primarily affected by soil fertilization type, rather than by the presence or absence of PFM. These results provide new insights into agricultural management strategies for improving soil carbon sequestration capacity.     

Endoscopically guided nasojejunal tube placement in dogs for short‐term postduodenal feeding

Objective – To evaluate a method for endoscopically guided nasojejunal tube placement allowing short‐term postduodenal feeding and chyme withdrawal in dogs. Design – Pilot study. Setting – University teaching hospital. Animals – Three healthy Beagle dogs with jejunal nipple valve fistulas. Interventions – After the dogs were anesthetized, an 8 Fr, 250‐cm polyvinyl chloride catheter was advanced through a gastroscope into the jejunum. Correct jejunal placement was established using endoscopic visualization and confirmed by fluoroscopy and radiography. The proximal end of the tube was pulled out through 1 nostril and sutured to the skin of the forehead. Thereafter, jejunal feeding was administered for 4 days. Follow‐up examinations included daily confirmation of the tube's position using radiography, physical examination, and blood analyses. Withdrawal of jejunal chyme was performed after jejunal and oral feeding. Measurements and Main Results – Fluoroscopic examination confirmed that endoscopic visualization alone allowed correct jejunal placement. During a 4‐day postduodenal feeding period, repeated radiographic examination revealed stable positioning of the tubes within the jejunum with minor cranial displacement. The tubes were functional throughout the study without causing identifiable problems. Repeated physical examinations and blood analysis showed no abnormalities. We were able to administer the daily caloric requirements as a liquid diet. Jejunal chyme was successfully withdrawn via the tube. Conclusions – Endoscopically guided nasojejunal tube placement was shown to be a minimally invasive, well‐tolerated method for short‐term jejunal feeding in healthy dogs. This technique is a viable option for dogs requiring jejunal feeding but not laparotomy. The feasibility of chyme sampling is another unique application of the procedure.