Three-dimensional modelling of mercury cycling in the Gulf of Trieste.

The Gulf of Trieste (Northern Adriatic) is subject to mercury pollution from a former mercury mine in Idrija, located along a river which transports mercury-contaminated sediments into the Gulf. Concentrations in suspended and bottom sediments are up to two orders of magnitude higher than in the central and southern Adriatic. Extensive research has been carried out on measurements and modelling of the transport and fate of mercury in the Gulf. Two- and three-dimensional models have been developed to include the influence of the significant advective transport due to currents. Wind, thermohaline forcing, and the Soca river momentum are the most important forcing factors. A two-dimensional model simulated the transport of non-methylated and methylated mercury in dissolved, particulate and plankton fractions. Mercury processes included the input of atmospheric mercury, sedimentation, reduction, methylation and demethylation. The model simulations gave basically what were proper trends of the phenomena; quantitatively the measured and computed results are mainly within a factor of three. To simulate the non-uniform distribution of parameters over the depth, an existing three-dimensional (3D) hydrodynamic and transport-dispersion (TD) model, PCFLOW3D, was adapted and applied. As it was found that most mercury transport is related to suspended sediment particles, a new 3D sediment transport module was also developed and included in the model. Three cases are presented: one describing the simulation of TD of dissolved total mercury; another the simulation of the TD of particulate mercury in the Gulf during a river flood; and the third simulating sediment transport in the Gulf during a period of strong ENE wind. Comparison with measurements was only partly possible, but mainly the computed and measured results were within a factor of two and proper trends of the phenomena were obtained by the simulations. The combination of modelling and measurements has resulted in some interesting conclusions about the phenomenon of the transport and fate of mercury in a coastal sea.

The neighborhood distribution effect in visual word recognition: words with single and twin neighbors.

Lexical-decision tasks were used to test the role of neighborhood distribution in visual word recognition. Predictions based on the interactive activation model were generated by running simulations. The data were compared for words with 2 higher frequency neighbors that differed in their neighborhood distribution. The neighbors were "single" when they did not share a neighborhood relationship (e.g., neighbors of flanc: flanc-blanc) or "twin" when they shared a neighborhood relationship (e.g., neighbors of firme: ferme-forme). Results show a facilitatory neighborhood distribution effect on words in Experiments 1 (easy pseudowords) and 3 (difficult pseudowords and easy pseudowords) and on pseudowords in Experiment 2. These data can be accounted for in terms of lexical inhibition in the interactive activation framework.

Mercury in contaminated coastal environments; a case study: the Gulf of Trieste.

Some general facts, uncertainties and gaps in current knowledge of Hg cycling in coastal and oceanic environments are given. As a case study the Gulf of Trieste is chosen. The Gulf is subject to substantial Hg pollution, originating from the Soca river, that drains the cinnabar deposits of the world's second largest Hg mining area, Idrija, Slovenia. The Gulf belongs to one of the most polluted areas in the Mediterranean. Apart from Hg problems, the Gulf is also a subject to industrial and sewage pollution. Due to deteriorating water quality in the Gulf there is a great concern that Hg can be remobilized from sediments to the water column as well as enhance methylation rates which may consequently increase already elevated Hg levels in aquatic organisms. The paper presents data from a recent study which aims to assess the extent of contamination of the Gulf of Trieste after the closure of the Hg mine. Mercury and methylmercury were measured in various environmental compartments (estuarine and marine waters, sediments, and organisms) during the period 1995-1997. Data obtained show that even 10 years after closure of the Hg mine, Hg concentrations in river sediments and water are still very high and did not show the expected decrease of Hg in the Gulf of Trieste. A provisional annual mercury mass balance was established for the Gulf of Trieste showing that the major source of inorganic mercury is still the River Soca (Isonzo) while the major source of methylmercury is the bottom sediment of the Gulf.

Supraglottic and pharyngeal sensory abnormalities in stroke patients with dysphagia.

Dysphagia and aspiration are two devastating sequelae of stroke, accounting for nearly 40,000 deaths from aspiration pneumonia each year in the United States. While motor deficits in the larynx and pharynx are thought responsible for dysphagia and aspiration in stroke patients, no prior study has evaluated whether these patients also have sensory deficits. The aim of this study was to evaluate the sensory capacity of the laryngopharynx (LP) in supratentorial or brain stem stroke patients who presented with dysphagia. Fifteen stroke patients (mean age, 66.7 +/- 13.8 [SD] years) were prospectively evaluated by means of our previously described method whereby air pulse stimuli were delivered via a flexible fiberoptic telescope to the mucosa innervated by the superior laryngeal nerve. There were 15 age-matched controls. No LP sensory deficits were found in any of the age-matched controls. In all stroke patients studied, either unilateral (n = 9) or bilateral (n = 6) sensory deficits were identified. Deficits were defined as either a moderate impairment in sensory discrimination thresholds (3.5 to 6.0 mm Hg) or a severe sensory impairment (> 6.0 mm Hg). These sensory discrimination thresholds were significantly greater than in age-matched controls (7.05 +/- 0.17 mm Hg for the supratentorial group and 6.05 +/- 1.22 mm Hg for the infratentorial group versus 2.61 +/- 0.69 mm Hg for the controls). Among patients with unilateral deficits, sensory thresholds were moderately to severely elevated in all 9 cases on the affected side compared with the unaffected side (p < .01, Fisher's exact test). Moreover, the sensory thresholds of the unaffected side were not significantly different from those of age-matched controls (2.51 +/- 0.25 mm Hg versus 2.61 +/- 0.69 mm Hg, respectively). All 6 patients with bilateral deficits had severe impairments. The results of an outcome assessment in 13 of 15 patients revealed that 2 out of 5 patients with moderate LP sensory impairment and 5 out of 8 with severe impairment developed aspiration. Our results show for the first time that stroke patients with dysphagia have significant sensory deficits in the LP and that these impairments are likely to contribute to the development of aspiration.

Usefulness of blood lactate as a predictor of shock development in acute myocardial infarction.

Data were obtained and analyzed in 229 patients admitted to the coronary care unit from November 1988 through July 1989. The patients were classified into 2 groups: patients without or with only mild left ventricular failure (Killip class I or II) during their hospital stay (group I), and patients who were in Killip class I or II on admission but developed cardiogenic shock during hospitalization (group II). Discriminant function analysis was performed using the following variables: patients' age, history of previous myocardial infarction, diabetes mellitus, blood lactate, urea, creatinine, creatine kinase, aspartate aminotransferase, lactate dehydrogenase concentrations, and chest x-ray cardiothoracic ratio. Variables that were found to significantly discriminate the 2 groups of patients were age, previous infarction, x-ray cardiothoracic ratio, blood urea and lactate concentrations. The risk index was computed, and blood lactate was the variable with the greatest predictive power for shock development. The sensitivity, specificity and predictive value of the risk index, taking various cutoff points, were calculated. With a cutoff value of 1, sensitivity was 65%, specificity 91%, positive predictive value 36% and negative predictive value 97%. With a cutoff value of 2, sensitivity was 53%, specificity 99%, positive predictive value 82% and negative predictive value 96%.