Hydrocarbon Contamination Patterns in the Cenotes of the Mexican Caribbean: The Application of Principal Component Analysis.

Cenotes are naturally occurring flooded caves that are frequent in Mexico's Yucatan Peninsula; they result from the collapse of limestone bedrock into the regional groundwater table. Cenotes in Quintana Roo are important ecological and economic hot spots but are susceptible to anthropogenic pollution. In this study, we collected water samples from 11 cenotes over multiple years to evaluate polycyclic aromatic hydrocarbon (PAH) concentrations and patterns as associated with tourist traffic. The primary PAHs detected in samples included fluoranthene, anthracene, phenanthrene and naphthalene, with total PAH concentrations increasing almost fivefold for cenotes sampled from 2016 to 2017. This is compared to only a 7% increase in tourist traffic during these years. Multivariate statistical analysis of the PAH concentration data suggests that diesel, gasoline and asphalt are the most likely pollution sources and that they are associated with periods of increased tourist traffic.

Short communication: Socio-psychological factors influencing dairy farmers' intention to adopt high-grain feeding in Brazil.

This study aimed to apply the theory of planned behavior to determine the effects of attitude, perceived behavioral control, and subjective norms on the intention of dairy farmers toward high-grain feeding. Quantitative data were collected through interviews with 150 dairy farmers in Paraná, Brazil. Partial least squares structural equation modeling was used to analyze the data. We observed that farmers with a positive perception of grain feeding (attitude) and a positive perception of their ability to increase the use of grains (perceived behavioral control) had higher intention to increase grain feeding. Social pressure (subjective norm) had no effect on the intention to grain feed. These results can contribute to the development of public strategies and policies that encourage the use of high-grain diets in dairy farms.

Competitive effects on mercury removal by an agricultural waste: application to synthetic and natural spiked waters.

In this work, the efficiency of a local and highly, available agricultural waste, the raw rice husk, was used to remove mercury (Hg) from synthetic and natural waters, spiked with concentrations that reflect the contamination problems found in the environment. Different operating conditions were tested, including initial pH, ionic strength, the presence of co-ions (cadmium) and organic matter. The sorption efficiency of rice husk was slightly affected by the presence H+ ions (pH range between 3 and 9), but in the presence of NaNO3 and NaCl electrolytes and in binary solutions containing Cd2+ and H2+, the sorption efficiency was dependent on the nature and levels of the interfering ion and on the initial concentration of Hg+ used. Nevertheless, in a situation of equilibrium the effect of those ions was negligible and the removal efficiency ranged between 82% and 94% and between 90% and 96% for an initial Hg2+ concentration of 0.05 mg L(-1) and 0.50 mg L(-1), respectively. In more complex matrices, i.e. in the presence ofhumic substances and in natural river waters, the speciation and dynamics of Hg was changed and a fraction of the metal becomes unavailable in solution. Even then, the values obtained for Hg removal were satisfactory, i.e. between 59% and 76% and 81% and 85% for an initial concentration of Hg2+ of 0.05 and 0.50 mg L(-1), respectively.

Representative elementary length to measure soil mass attenuation coefficient.

With increasing demand for better yield in agricultural areas, soil physical property representative measurements are more and more essential. Nuclear techniques such as computerized tomography (CT) and gamma-ray attenuation (GAT) have been widely employed with this purpose. The soil mass attenuation coefficient (µ(s)) is an important parameter for CT and GAT analysis. When experimentally determined (µ(es)), the use of suitable sized samples enable to evaluate it precisely, as well as to reduce measurement time and costs. This study investigated the representative elementary length (REL) of sandy and clayey soils for µ(es) measurements. Two radioactive sources were employed ((241)Am and (137)Cs), three collimators (2-4 mm diameters), and 14 thickness (x) samples (2-15 cm). Results indicated ideal thickness intervals of 12-15 and 2-4 cm for the sources (137)Cs and (241)Am, respectively. The application of such results in representative elementary area (REA) evaluations in clayey soil clods via CT indicated that µ(es) average values obtained for x > 4 cm and source (241)Am might induce to the use of samples which are not large enough for soil bulk density evaluations (ρ(s)). As a consequence, ρ(s) might be under- or overestimated, generating inaccurate conclusions about the physical quality of the soil under study.

Neurotropism and neuropathological effects of selected rhabdoviruses on intranasally-infected newborn mice.

Viral neurotropism is the ability of viruses to infect neuronal cells. This is well studied for herpesviruses, rabies-related viruses, and a few others, but it is poorly investigated among almost all arboviruses. In this study, we describe both the neurotropism and the neuropathological effects of Amazonian rhabdoviruses on the brains of experimentally infected-newborn mice. Suckling mice were intranasally infected with 10(-4) to 10(-8) LD50 of viruses. Animals were anaesthetized and perfused after they had become sick. Immunohistochemistry using specific anti-virus and anti-active caspase three antibodies was performed. All infected animals developed fatal encephalitis. Survival time ranged from 18 h to 15 days. Viruses presented distinct species-dependent neurotropism for CNS regions. Histopathological analysis revealed variable degrees of necrosis and apoptosis in different brain regions. These results showed that viruses belonging to the Rhabdoviridae family possess distinct tropism for CNS structures and induce different pattern of cell death depending on the CNS region.

Ipsilateral neck cancer recurrences after elective supraomohyoid neck dissection.

DESIGN: Retrospective analysis of a case series. SETTING: Referral center, private or institutional practice, hospitalized care. OBJECTIVE: To analyze the level (site) of ipsilateral neck recurrences after supraomohyoid (SOH) dissection in patients with lip, oral, and oropharyngeal cancer treated in a single institution. INTERVENTION: Supraomohyoid neck dissection. PATIENTS AND METHODS: From 1979 to 1997, 154 patients with oral and oropharyngeal carcinoma and no palpable lymph nodes at the neck underwent ipsilateral elective SOH dissection. RESULTS: Tumor sites were the lip, 5 cases (3.3%); oral cavity, 128 cases (83.1%); and oropharynx, 21 cases (13.6%). Tumor stages were T1, 13 cases (8.4%); T2, 77 cases (50.0%); T3, 40 cases (27.0%); and T4, 22 cases (14.3%). There were 7 cases (4.5%) of ipsilateral neck recurrences. Three were beyond the limits of the SOH dissection, and 4 were inside these limits. There was no association of neck recurrences with the pathological status of the lymph nodes. Six of the 7 recurrences were in patients who underwent postoperative radiotherapy. CONCLUSIONS: The incidence of neck recurrence after selective neck dissection was 4.5%, and it occurred either inside (57.1%) or beyond (42.9%) the limits of the selective neck dissection.