A model study of convergent dynamics in the marginal ice zone.

With the increasing resolution of operational forecasting models, the marginal ice zone (MIZ), the area where waves and sea ice interact, can now be better represented. However, the proper mechanics of wave propagation and attenuation in ice, and especially their influence on sea ice dynamics, still remain poorly understood and constrained in models. Observations have shown exponential wave energy decrease with distance in sea ice, particularly strong at higher frequencies. Some of this energy is transferred to the ice, breaking it into smaller floes and weakening it, as well as exerting a stress on the ice similar to winds and currents. In this article, we present a one-dimensional, fully integrated wave and ice model that has been developed to test different parameterizations of wave-ice interactions. The response of the ice cover to the wind and wave radiative stresses is investigated for a variety of wind, wave and ice conditions at different scales. Results of sensitivity analyses reveal the complex interplay between wave attenuation and rheological parameters and suggest that the compressive strength of the MIZ may be better represented by a Mohr-Coulomb parameterization with a nonlinear dependence on thickness. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'.

Accelerometer tags: detecting and identifying activities in fish and the effect of sampling frequency.

Monitoring and measuring the behaviour and movement of aquatic animals in the wild is typically challenging, though micro-accelerometer (archival or telemetry) tags now provide the means to remotely identify and quantify behavioural states and rates such as resting, swimming and migrating, and to estimate activity and energy budgets. Most studies use low-frequency (≤32 Hz) accelerometer sampling because of battery and data-archiving constraints. In this study we assessed the effect of sampling frequency (aliasing) on activity detection probability using the great sculpin (Myoxocephalus polyacanthoceaphalus) as a model species. Feeding strikes and escape responses (fast-start activities) and spontaneous movements among seven different great sculpin were triggered, observed and recorded using video records and a tri-axial accelerometer sampling at 100 Hz. We demonstrate that multiple parameters in the time and probability domains can statistically differentiate between activities with high detection (90%) and identification (80%) probabilities. Detection probability for feeding and escape activities decreased by 50% when sampling at <10 Hz. Our analyses illustrate additional problems associated with aliasing and how activity and energy-budget estimates can be compromised and misinterpreted. We recommend that high-frequency (>30 Hz) accelerometer sampling be used in similar laboratory and field studies. If battery and/or data storage is limited, we also recommend archiving the events via an on-board algorithm that determines the highest likelihood and subsequent archiving of the various event classes of interest.

Impact of grass and grass with poplar buffer strips on atrazine and metolachlor losses in surface runoff and subsurface infiltration from agricultural plots.

In many areas of intensive corn production, atrazine and metolachlor are among the most commonly found herbicides in surface and ground water. This 2-yr study compared the impact of grass and grass+tree buffer strips on the exported masses of atrazine, metolachlor, and a degradation product of atrazine, desethylatrazine (DEA). The experimental system consisted of four replicate plots in a three-way completely randomized design (no buffer zone, grass buffer zone, and grass+tree buffer strips). The field plots were 5 m wide and 30 m long and grown in corn. The grass and grass+tree buffer strips were 5 m and had the same grass vegetation except for eight young hybrid poplars. Over the 2-yr study, surface runoff and subsurface infiltration water (under the buffer strip) were collected after the initial three rainfall events after herbicide application. Dissolved atrazine, metolachlor, and DEA were analyzed by gas chromatography/mass spectrometry. The presence of buffer strips decreased the exported masses of atrazine and metolachlor in surface runoff. A three-way ANOVA with treatment (type of buffer strip), water (surface runoff or subsurface infiltration), and time between herbicide application and rainfall event as factors showed a significant reduction (40-60% in 2004 and 75-95% in 2005) in the total (surface runoff+infiltrated water) exported masses of atrazine and metolachlor in the presence of buffer strips. Rainfall events after herbicide application were different between the 2 yr and greatly affected the flow distribution (e.g., subsurface infiltration) and the leached herbicide concentrations. No significant difference in the capacity to reduce herbicide exports was observed between grass and grass+tree buffer strip treatments; the poorly developed young poplar biomass at the time of the study may partly explain this observation.

Serum eosinophil cationic protein: a marker of disease activity in Churg-Strauss syndrome.

The cytotoxic proteins released by activated eosinophils should play a role in the development of Churg-Strauss syndrome (CSS). Eighteen patients (15 males and 3 females, age 41 +/- 13.3 years) with CSS according to the American College of Rheumatology criteria were included in the study. Thirteen serum samples from 11 patients were obtained at the time of disease flare, and the sera from 6 of them were also obtained at the time of clinical remission. Sera from seven other patients were obtained in clinical remission. Anti-neutrophil cytoplasm antibodies were detected in four (22.2%) patients. Fifteen healthy individuals were used as controls. Mean eosinophil count differed significantly between CSS patients with active disease and patients in clinical remission (3,407/mm(3) vs. 258/mm(3); P < 0.01), between CSS patients with active disease and healthy individuals (3,407/mm(3) vs. 211/mm(3); P < 0.01). Mean serum ECP levels differed significantly between patients with active or inactive disease (219 microg/L vs. 56.8 microg/L; P < 0.0001), between patients with active disease and healthy individuals (219 microg/L vs. 26.2 microg/L; P < 0.0001), but not between patients with inactive disease and healthy individuals (ns). Peripheral blood eosinophils count correlated with serum ECP during CSS flares disease (R = 0.6264; P < 0.05) and during periods of remission (R = 0.4798; P < 0.05). Our results support that ECP might be used as a disease activity marker in CSS.

[Management of blood eosinophilia in an outpatient clinic for tropical diseases]. / Prise en charge des hyperéosinophilies sanguines dans une consultation de maladies tropicales.

OBJECTIVE: We assessed the frequency of parasitic diseases and the efficacy of presumptive treatment when no cause was found. MATERIALS AND METHODS: This prospective study took place in the Tropical Disease department of Bicêtre Hospital over a two-year period and included patients with eosinophil counts exceeding 500/mm(3). RESULTS: The study included 117 patients with blood eosinophilia. A parasitic infection was identified for 48 (41%), and appropriate treatment resulted in a return to normal eosinophil counts for all of them. No parasite was identified in 45 patients (38.5%), but parasitic disease was suspected on the basis of clinical or epidemiologic evidence. These patients received presumptive treatment with antiparasitic drugs (ivermectin, albendazole and praziquantel, alone or in combination). Of the 30 patients in this group not lost to follow-up, eosinophil counts returned to normal for 20. Finally, a cause other than parasitosis was suspected for 15 of the 117 patients (13%): 9 (7.5%) of them were lost to follow-up. DISCUSSION: Parasites remain the leading cause of blood eosinophilia. Because the sensitivity of additional testing for these parasites is low and these antiparasitic drugs are safe (except for patients with loiasis), presumptive treatment appears appropriate.

Differential effects of sulphonylureas on the vasodilatory response evoked by K(ATP) channel openers.

The potency of three sulphonylureas, glibenclamide, glimepiride and gliclazide in antagonizing the vasorelaxant action of openers of adenosine triphosphate (ATP)-regulated K+ channel (KATP) was studied in vivo and in vitro in micro- and macrovessels, respectively. In the hamster cheek pouch, the vasodilatation and the increase in vascular diameter and blood flow induced by diazoxide were markedly reduced by the addition of either glibenclamide or glimepiride (0.8 microm) while they were not affected by gliclazide up to 12 microm. Similarly, in rat and guinea-pig isolated aortic rings, glibenclamide, glimepiride and gliclazide reduced the vasodilator activity of cromakalim. However, the inhibitory effect of gliclazide was considerably less when compared with either glimepiride or glibenclamide. These results suggest that, in contrast to glibenclamide and glimepiride, therapeutically relevant concentrations of gliclazide do not block the vascular effects produced by KATP channel openers in various in vitro and in vivo animal models.

Photoinduced oxidation of Hg0(aq) in the waters from the St. Lawrence estuary.

The oxidation of volatile aqueous Hg0 in aquatic systems may be important in decreasing the fluxes of Hg out of the water column. Using incubations of natural samples from the St. Lawrence River, we examined some of the parameters that control this oxidation. Hg0 was found to be chiefly mediated by UV radiation since (i) "dark" oxidation was not found to be statistically significant; (ii) visible light induced a significant but slow photooxidation (k = 0.09 h(-1)); and (iii) visible + UV radiation led to a faster photooxidation (k = 0.6-0.7 h(-1)), mainly because of UV-A induced reactions. Doubling UV irradiation did not increase the reaction rate of Hg0 photooxidation in natural water samples, indicating that some factor other than photon flux was rate limiting and suggesting that the reaction involves intermediate photoproduced oxidant(s). The addition of methanol, a *OH scavenger, decreased Hg photooxidation rates by 25% in brackish waters and by 19% in artificial saline water containing semiquinones, indicating that *OH may be partly responsible for Hg0 oxidation. Photooxidation rates were not affected by oxygen concentrations and did not decrease when samples were heat-sterilized, treated with chloroform, or filtered prior to exposure to light.