Iron-rich post-perovskite and the origin of ultralow-velocity zones

The boundary layer between the crystalline silicate lower mantle and the liquid iron core contains regions with ultralow seismic velocities. Such low compressional and shear wave velocities and high Poisson's ratio are also observed experimentally in post-perovskite silicate phase containing up to 40 mol% FeSiO3 endmember. The iron-rich post-perovskite silicate is stable at the pressure-temperature and chemical environment of the core-mantle boundary and can be formed by core-mantle reaction. Mantle dynamics may lead to further accumulation of this material into the ultralow-velocity patches that are observable by seismology.     

Distribution and activity of hypolithic soil crusts in a hyperarid desert (Baja California, Mexico)

Widespread and ecologically important, biological soil crusts include those microbial communities living on the surface of the soil and those that live beneath semitranslucent rocks (a.k.a. hypolithic crusts). We examined the distribution, abundance, physiology, and potential soil N contributions of hypolithic, biological crusts in hyperarid ecosystems of the Baja California peninsula and islands in the midriff region of the Gulf of California, Mexico (Sonoran desert). Crusts were limited in distribution to areas with translucent quartz rocks less than 3 cm thick, were not found on areas of islands with seabird guano deposition, but covered as much as 1% (12,750 m²) of the surface area of one island. The percent of available rocks colonized by crusts was similar between the mainland (38%) and islands without seabird guano (26%). Carbon fixation rates in the field, which have not been previously reported, ranged between 0 and 1.23 μmol m⁻² s⁻¹, and in the lab ranged between 0.66 and 0.94 μmol m⁻² s⁻¹. Evidence of low rates of N fixation was inferred from δ ¹⁵N values of crust and soil. Hypolithic crusts were found to have minimal, if any, influence on soil salinity, pH, and , but may represent up to 14% of the biomass of primary producers on these islands and provide C and N to the belowground and possibly aboveground heterotrophic communities where crusts exist. The results of this study suggest a limited but potentially important contribution of hypolithic soil crusts to hyperarid ecosystems.     

Field dissipation and environmental hazard assessment of clomazone, molinate, and thiobencarb in Australian rice culture

The fates of clomazone [2-(2-chlorophenyl)methyl-4,4-dimethyl-3-isoxazolidinone], molinate (S-ethyl hexahydro-1-H-azepine-1-carbothioate), and thiobencarb {S-[(4-chlorophenyl)methyl]diethylcarbamothioate} applied to rice were studied at two locations in New South Wales (Australia). Rates of dissipation (DT50) from floodwaters and soils were measured. Dissipation of the three herbicides from water and soil can be best explained by a first-order decay process. DT(50) values for clomazone, molinate, and thiobencarb were 7.2, 5.1, and 3.5 days, respectively, in water and 14.6, 23.9, and >46 days, respectively, in surface soil. Maximum measured concentrations of clomazone, molinate, and thiobencarb in floodwaters were 202, 1042, and 148 microg/L, respectively, taking 18.4, 26.4, and 21.4 days to dissipate to concentrations set to protect aquatic ecosystems. A hazard assessment identified clomazone as presenting a low environmental hazard while molinate and thiobencarb presented a medium environmental hazard when used at registered field rates.     

Larval calcification and growth of veligers to early pediveliger of the queen conch Strombus gigas in mesocosm and laboratory conditions

The goals of this study were to evaluate growth, development, and calcification process of veligers of Strombus gigas grown in natural conditions in mesocosm versus laboratory conditions. In this study, larvae bred in mesocosm conditions had a good growth rate (33.3±12.40 μm.day^?1) when fed with natural phytoplankton in natural flowing seawater versus a lower growth rate of 8.8±5.20 μm.day^?1 for larvae reared in laboratory conditions and fed with a monoalgal diet of Nannochloropsis oculata. Physicochemical parameters did not explain the difference on larval growth in both culture systems according to the principal component analysis done. Raman microspectrometry carried out on conch larvae grown in mesocosm and lab conditions allowed us to emphasize the biosynthesis of calcium carbonate species and their structure type evolution (amorphous, aragonite, or calcite structure) as a function of the breeding time by detecting and identifying in the spectra the characteristic Raman bands of CO₃ chemical groups and lattice vibrations. This analytical method seems to indicate that crystalline CaCO₃ structures are not detected in the recorded spectra on larvae reared in laboratory conditions during the early stages of the shell construction of 1 to 8 days. For this reason, light and current flow have also been considered in the discussion that can help to explain the differences found in this study. Contrarily, the Raman spectra acquired on larvae grown in mesocosms exhibit characteristic bands of aragonite (CO₃ double peak at 697–701 cm^?1 and lattice vibrations at 170 and 220 cm^?1) from the third day of breeding. The best shell growth and shell calcification pointed out in larvae grown in mesocosm compared to laboratory conditions are probably due to the nutrient amounts present in the food available in mesocosm.

     

Cross‐Sectional Study of the Prevalence of Radiographic Degenerative Joint Disease in Domesticated Cats

Objective: To determine the prevalence of radiographic signs of degenerative joint disease (DJD) in a randomly selected sample of domestic cats. Study Design: Prospective observational study. Animals: Client‐owned cats. Methods: Cats (n=100) from a single practice and equally distributed across 4 age groups (0–5; 5–10; 10–15, and 15–20 years old) were randomly selected (regardless of heath status) and sedated for orthogonal radiographic projections of all joints and the spine. Quasi‐Poisson regression analysis was used to investigate the relationship between patient demographics, blood biochemistry, hematologic and urine analysis variables, and DJD severity. Results: Most (92%) cats had radiographic evidence of DJD; 91% had at least 1 site of appendicular DJD and 55% had ≥1 site of axial column DJD. Affected joints in descending order of frequency were hip, stifle, tarsus, and elbow. The thoracic segment of the spine was more frequently affected than the lumbosacral segment. Although many variables were significantly associated with DJD, when variables were combined, only the association between age and DJD was significant (P<.0001). For each 1‐year increase in cat age, the expected total DJD score increases by an estimated 13.6% (95% confidence interval: 10.6%, 16.8%). Conclusion: Radiographically visible DJD is very common in domesticated cats, even in young animals and is strongly associated with age. Clinical Relevance: DJD is a common disease of domesticated cats that requires further investigation of its associated clinical signs.     

Determination of methyl bromide residues in stored foods using automated headspace gas chromatography

An automated gas chromatographic headspace method capable of detecting methyl bromide (MB) down to 0.01 mg kg^?1 has been developed and evaluated. The method is suitable for analysing cereals, nuts, seeds and dried fruit. Commodities are extracted with solvent and MB present is derivatised to methyl iodide (MI) which is determined by automated headspace gas chromatography. Results from the method described are compared with those using an established solvent extraction method and show good quantitative agreement. The analytical conditions recommended are likely to be suitable for examination of other commodities for MB residues.     

The fate and insecticidal activity of pirimiphos-methyl in stored wheat grain

The degradation of [¹⁴C]pirimiphos-methyl was investigated on a 1-kg bulk of grain stored in the laboratory at 15°C for 28 weeks. Breakdown of pirimiphos-methyl was slow, leaving 77% of the applied dose unchanged at the end of the experiment. The major degradation product was the hydroxypyrimidine (up to 12.5% of the applied dose) with the remainder of the residue (up to 12.1%) remaining within the grain tissues after solvent extraction. The efficacy of the treatment was assessed in a parallel experiment by bioassay of a 5-kg bulk of grain dosed with unlabelled pirimiphos-methyl. 100% Mortality of an organophosphateresistant strain of Oryzaephilus surinamensis L. was maintained throughout the experiment whereas some survival of an organophosphate-resistant strain of Tribolium castanewm (Herbst) occurred after 12 weeks of storage. This increased to give a 20% survival rate at the end of the experiment.     

Cardiac toxicity from phenylpropanolamine overdose in a dog

A 5-year-old, 29-kg, female Labrador retriever developed tachypnea, tachycardia, and ataxia following ingestion of approximately 48 mg/kg of phenylpropanolamine. Initial diagnostic tests showed multiform ventricular tachycardia, left ventricular dilatation with a focal dyskinetic region in the dorsal interventricular septum, and elevations in creatinine kinase and cardiac troponin I. All abnormalities resolved within 6 months. The transient electrocardiographic, echocardiographic, and biochemical abnormalities were consistent with myocardial necrosis from infarction or direct catecholamine-induced myocardial toxicity.     

Effective periodontal disease control using dental hygiene chews

This study evaluated the effectiveness of a newly developed dental hygiene chew for dogs, with and without a natural antimicrobial additive, compared with a reference diet. Efficacy was determined by measuring the severity of gingivitis and the accumulation of dental plaque and calculus in dogs after 4-weeks of being fed the different dietary regimens. Dogs fed a single daily dental chew had significantly less gingivitis (P = 0. 02), plaque (P = 0. 0004), and calculus (P = 0.0001) compared with dogs in the control group that were fed an identical diet but received no chews. The inclusion of the antimicrobial agent did not improve the efficacy of the product. The dental hygiene chews tested in this study have potential to help reduce the incidence of periodontal disease in dogs.