The Effect of Natural Dissolved Organic Carbon on the Acute Toxicity of Copper to Larval Freshwater Mussels (\u3cem\u3eGlochidia\u3c/em\u3e)

The present study examined the effect of dissolved organic carbon (DOC), both added and inherent, on Cu toxicity in glochidia, the larvae of freshwater mussels. Using incremental additions of natural DOC concentrate and reconstituted water, a series of acute copper toxicity tests were conducted. An increase in DOC from 0.7 to 4.4 mg C/L resulted in a fourfold increase (36–150 μg Cu/L) in the 24-h median effective concentration (EC50) and a significant linear relationship (r2=0.98, p=0.0008) between the DOC concentration and the Cu EC50 of Lampsilis siliquoidea glochidia. The ameliorating effect of added DOC on Cu toxicity was confirmed using a second mussel species, the endangered (in Canada) Lampsilis fasciola. The effect of inherent (i.e., not added) DOC on Cu toxicity was also assessed in eight natural waters (DOC 5–15 mg C/L). These experiments revealed a significant relationship between the EC50 and the concentration of inherent DOC (r2=0.79, p=0.0031) with EC50s ranging from 27 to 111 μg Cu/L. These laboratory tests have demonstrated that DOC provides glochidia with significant protection from acute Cu toxicity. The potential risk that Cu poses to mussel populations was assessed by comparing Cu and DOC concentrations from significant mussel habitats in Ontario to the EC50s. Although overall mean Cu concentration in the mussel’s habitat was well below the acutely toxic level given the concentration of DOC, episodic Cu releases in low DOC waters may be a concern for the recovery of endangered freshwater mussels. The results are examined in the context of current Cu water quality regulations including the U.S. Environmental Protection Agency’s (U.S. EPA) biotic ligand model

March of the Green Iguana : Non-native Distribution and Predicted Geographic Range of Iguana iguana in the Greater Caribbean Region

Green Iguanas (Iguana iguana L. 1758) have been introduced outside their native range largely through the pet trade. In many places, exotic populations have invaded and many have become established. Of special concern is the Greater Caribbean Basin, where several exotic populations of Green Iguanas have had a negative impact, and may threaten the conservation of several native species, including possible native and distinct forms of I. iguana in the Lesser Antilles, and the endangered Lesser Antilles Iguana (I. delicatissima Laurenti 1768). We assessed the risk of spread and invasion by Green Iguanas in the Greater Caribbean Basin using the maximum entropy niche-modeling algorithm (MaxEnt) to predict the potential distribution of this reptile. We used a total of 187 location points that represented occurrences from both the native and the invasive range, coupled with environmental data as predictor variables. Our model had average training and test AUC values of 0.90 and 0.87 respectively, indicating a high predictive ability. The model predicts suitable conditions for I. iguana in south and central Florida (mainly along the coast), and in regions of all the islands in the Caribbean. Given the known negative impact of Green Iguanas and their dispersal capabilities, governments in the Greater Caribbean Basin should manage non-native populations to prevent further spread, and revise and enact laws that allow management agencies to respond quickly in the case of new Green Iguana incursions

Cirrus microphysics and radiative transfer: Cloud field study on October 28, 1986

The radiative properties of cirrus clouds present one of the unresolved problems in weather and climate research. Uncertainties in ice particle amount and size and, also, the general inability to model the single scattering properties of their usually complex particle shapes, prevent accurate model predictions. For an improved understanding of cirrus radiative effects, field experiments, as those of the Cirrus IFO of FIRE, are necessary. Simultaneous measurements of radiative fluxes and cirrus microphysics at multiple cirrus cloud altitudes allows the pitting of calculated versus measured vertical flux profiles; with the potential to judge current cirrus cloud modeling. Most of the problems in this study are linked to the inhomogeneity of the cloud field. Thus, only studies on more homogeneous cirrus cloud cases promises a possibility to improve current cirrus parameterizations. Still, the current inability to detect small ice particles will remain as a considerable handicap

Modeling the R2* relaxivity of blood at 1.5 Tesla

BOLD (Blood Oxygenation Level Dependent) imaging is used in fMRI to show differences in activation of the brain based on the relative changes of the T2* (= 1/R2*) signal of the blood. However, quantification of blood oxygenation level based on the T2* signal has been hindered by the lack of a predictive model which accurately correlates the T2* signal to the oxygenation level of blood. The T2* signal decay in BOLD imaging is generated due to blood containing paramagnetic deoxyhemoglobin (in comparison to diamagnetic oxyhemoglobin). This generates local field inhomogeneities, which cause protons to experience different phase shifts, leading to dephasing and the MR signal decay. The blood T2* signal has been shown to decay with a complex behavior1, termed Non-Lorenztian, and thus is not adequately described by the traditional model of simplemono-exponential decay. Theoretical calculations show that diffusion narrowing substantially affects signal loss in our data. Over the past decade, several theoretical models have been proposed to describe this Non-Lorenztian behavior in the blood T2* signal in BOLD fMRI imaging. The goal of this project was to investigate different models which have been proposed over the years and determine a semi-phenomenological model for the T2* behaviorusing actual MR blood data

Retrospective Analysis of Factors Leading to Pediatric Tracheostomy Decannulation Failure. A Single-Institution Experience

RATIONALE: There is a lack of evidence regarding factors associated with failure of tracheostomy decannulation. OBJECTIVES: We aimed to identify characteristics of pediatric patients who fail a tracheostomy decannulation challenge Methods: A retrospective review was performed on all patients who had a decannulation challenge at a tertiary care center from June 2006 to October 2013. Tracheostomy decannulation failure was defined as reinsertion of the tracheostomy tube within 6 months of the challenge. Data on demographics, indications for tracheostomy, home mechanical ventilation, and comorbidities were collected. Data were also collected on specific airway endoscopic findings during the predecannulation bronchoscopy and airway surgical procedures before decannulation. We attempted to predict the decannulation outcome by analyzing associations. MEASUREMENTS AND MAIN RESULTS: 147 of 189 (77.8%) patients were successfully decannulated on the first attempt. Tracheostomy performed due to chronic respiratory failure decreased odds for decannulation failure (odds ratio = 0.34, 95% confidence interval = 0.15-0.77). Genetic abnormalities (45%) and feeding dysfunction (93%) were increased in the population of patients failing their first attempt. The presence of one comorbidity increased the odds of failure by 68% (odds ratio = 1.68, 95% confidence interval = 1.23-2.29). Decannulation pursuit based on parental expectation of success, rather than medically determined readiness, was associated with a higher chance of failure (P = 0.01). CONCLUSIONS: Our study highlights the role of genetic abnormalities, feeding dysfunction, and multiple comorbidities in patients who fail decannulation. Our findings also demonstrate that the outcome of decannulation may be predicted by the indication for tracheostomy. Patients who had tracheostomy placed for chronic respiratory support had a higher likelihood of success. Absence of a surgically treatable airway obstruction abnormality on the predecannulation bronchoscopy increased the chances of success

Enhancement of cloud cover and suppression of nocturnal drizzle in stratocumulus polluted by haze

Recent satellite observations indicate a significant decrease of cloud water in ship tracks, in contrast to an ensemble of in situ ship-track measurements showing no average change in cloud water relative to the surrounding clouds, and contrary to the expectation of cloud water increasing in polluted clouds. We find through large-eddy simulations of stratocumulus that the trend in the satellite data is likely an artifact of sampling only overcast clouds. The simulations instead show cloud cover increasing with droplet concentrations. The simulations also show that increases in cloud water from suppressing drizzle by increasing droplet concentrations are favored at night or at extremely low droplet concentrations.Keywords: Remote sensing, Meteorology and Atmospheric Dynamic

Future challenges of occupational safety and health policy-making in the UK

Understanding the changing landscape of occupational safety and health (OSH) regulation and standards and its implications are of central importance for ensuring that OSH outcomes are not compromised and the needs of different types of organizations are met. It is also important for developing appropriate strategies to anticipate and deal with future challenges for OSH policy-making. This paper draws on findings from two qualitative studies with key OSH stakeholders in the UK that were conducted as part of a research programme funded the Institution of Occupational Safety & Health. The aim of the first study was to elicit the views of key stakeholders on changes in the current OSH landscape so as to understand the nature and implications of these changes. The second study explored stakeholder perspectives on how to secure the optimal OSH landscape in the UK by addressing key future challenges for OSH policy-making

Anesthesia and Patients with Congenital Hyposensitivity to Pain

Background: Congenital hyposensitivity to pain or hereditary sensory and autonomic neuropathy represents a variety of disorders characterized by decreased perception of nociception, loss of other modalities of sensation, and variable expression of autonomic dysfunction. Sensory loss, especially that of pain, is associated with self-mutilations that may require frequent operations. Little is known about the safety of anesthesia for these patients. Methods: The authors performed a computerized search of the Mayo Clinic medical records database between January 1996 and November 2005 for patients with congenital hyposensitivity to pain and related disorders who underwent general anesthesia. Medical records were reviewed for demographics, anesthetic techniques and agents, use of opioids, and perioperative complications. In addition, the authors conducted a comprehensive review of the literature to summarize the current knowledge regarding anesthesia for patients with congenital hyposensitivity to pain, and compared it with the patients with hyposensitivity to pain identified at the Mayo Clinic. Results: The authors identified seven patients with hereditary sensory and autonomic neuropathy II, IV, or V and undefined variants of congenital pain hyposensitivity who generated 17 anesthesia records: 12 for orthopedic operations, 3 for sural nerve biopsies, and 2 for ophthalmologic procedures. In all patients, standard doses of volatile agents were used during anesthesia. Small amounts of opioids were used during the course of eight operations. Most patients experienced mild hypothermia (lowest temperature 34.7°C), and none experienced hyperthermia. All patients were hemodynamically stable during otherwise uneventful anesthesia. During recovery from anesthesia, opioids were given to only one patient, a single dose of 1 mg morphine. Even after major orthopedic operations, the patient did not require additional analgesia. Conclusions: The patients with profound congenital hyposensitivity to pain underwent anesthesia without any adverse events. The authors found that despite reduced pain perception, the requirements for volatile anesthetics were within the expected range for population with normal pain perception, but they did not require opioids postoperatively. Intraoperative mild hypothermia was easily managed by adjustment of environmental temperature