Phytoplankton competition in deep biomass maximum

Resource competition in heterogeneous environments is still an unresolved problem of theoretical ecology. In this article I analyze competition between two phytoplankton species in a deep water column, where the distributions of main resources (light and a limiting nutrient) have opposing gradients and co-limitation by both resources causes a deep biomass maximum. Assuming that the species have a trade-off in resource requirements and the water column is weakly mixed, I apply the invasion threshold analysis (Ryabov and Blasius 2011) to determine relations between environmental conditions and phytoplankton composition. Although species deplete resources in the interior of the water column, the resource levels at the bottom and surface remain high. As a result, the slope of resources gradients becomes a new crucial factor which, rather than the local resource values, determines the outcome of competition. The value of resource gradients nonlinearly depend on the density of consumers. This leads to complex relationships between environmental parameters and species composition. In particular, it is shown that an increase of both the incident light intensity or bottom nutrient concentrations favors the best light competitors, while an increase of the turbulent mixing or background turbidity favors the best nutrient competitors. These results might be important for prediction of species composition in deep ocean.Comment: 13 pages, 7 figures; Theoretical Ecology 201

Staphylococcal Toxic Shock Syndrome 2000–2006: Epidemiology, Clinical Features, and Molecular Characteristics

Circulating strains of Staphylococcus aureus (SA) have changed in the last 30 years including the emergence of community-associated methicillin-resistant SA (MRSA). A report suggested staphylococcal toxic shock syndrome (TSS) was increasing over 2000-2003. The last population-based assessment of TSS was 1986.Population-based active surveillance for TSS meeting the CDC definition using ICD-9 codes was conducted in the Minneapolis-St. Paul area (population 2,642,056) from 2000-2006. Medical records of potential cases were reviewed for case criteria, antimicrobial susceptibility, risk factors, and outcome. Superantigen PCR testing and PFGE were performed on available isolates from probable and confirmed cases.Of 7,491 hospitalizations that received one of the ICD-9 study codes, 61 TSS cases (33 menstrual, 28 non-menstrual) were identified. The average annual incidence per 100,000 of all, menstrual, and non-menstrual TSS was 0.52 (95% CI, 0.32-0.77), 0.69 (0.39-1.16), and 0.32 (0.12-0.67), respectively. Women 13-24 years had the highest incidence at 1.41 (0.63-2.61). No increase in incidence was observed from 2000-2006. MRSA was isolated in 1 menstrual and 3 non-menstrual cases (7% of TSS cases); 1 isolate was USA400. The superantigen gene tst-1 was identified in 20 (80%) of isolates and was more common in menstrual compared to non-menstrual isolates (89% vs. 50%, p = 0.07). Superantigen genes sea, seb and sec were found more frequently among non-menstrual compared to menstrual isolates [100% vs 25% (p = 0.4), 60% vs 0% (p<0.01), and 25% vs 13% (p = 0.5), respectively].TSS incidence remained stable across our surveillance period of 2000-2006 and compared to past population-based estimates in the 1980s. MRSA accounted for a small percentage of TSS cases. tst-1 continues to be the superantigen associated with the majority of menstrual cases. The CDC case definition identifies the most severe cases and has been consistently used but likely results in a substantial underestimation of the total TSS disease burden

Identification des facteurs influençant le délai d'admission hospitalière après accident vasculaire cérébral ischémique : Etude d'une population rurale

We studied the time of arrival of 235 consecutive patients admitted to the emergency department of a University Hospital located in a rural area after the first symptoms of ischemic stroke or TIA. Among the following factors, we determined those that might be involved in delayed admission: place of symptom onset, time and place of onset of the first symptoms, contact with a general practitioner before admission time, mode of transportation, clinical score, impairment of consciousness, presence of seizures, heart complaints or headache, age and past medical history of cerebrovascular, cardiovascular and hypertension diseases. Half of the patients arrived within 4 h 10 of symptom discovery and 55 p. cent arrived within 6 hours. The percentage of patients arriving within 3 h (p = 0.001) and 6 h (p = 0.001) was higher for those who had a stroke during the day (8 a.m.-8 p.m.) than during the evening and night. The other characteristics associated with a shorter delay included a low neurological score on the Mathew's Stroke Scale (p < 0.001 at 3 h and p = 0.001 at 6 h) and younger age (p = 0.015 at 3 h). Presence of headache delayed admission (p = 0.010). Forty-five percent of patients arrive at the hospital 6 hours after the discovery of symptoms, too late to receive optimal stroke therapy. Widespread public education on stroke is necessary to reduce the delay of admission, particularly for old patients and in case of mild to moderate deficits

Substitution of 11C-methionine PET by perfusion MRI during the follow-up of treated high-grade gliomas: Preliminary results in clinical practice.

PURPOSE: Our aim was to compare perfusion magnetic resonance imaging (MRI) and positron emission tomography (PET) using carbon-11 labelled methionine (MET) in gliomas and their value in differentiating tumour recurrence from necrosis. MATERIALS AND METHODS: We retrospectively reviewed 28 patients with a high-grade glioma. A total of 33MR perfusions and MET-PET were ultimately analysable for comparison between the relative cerebral blood volume (rCBV) and MET-PET examinations. Intra- and interobserver reproducibility was assessed and diagnostic value of rCBV compared to MET-PET and histology was assessed by the area under the receiver operating characteristic (ROC) curve. RESULTS: ROC curve analysis showed that rCBV had at least equal performances in differentiating tumour recurrence and necrosis than MET-PET. Cut-off value of rCBV for differentiating tumour from necrosis was 182% with a sensitivity of 81.5% and a specificity of 100%. CONCLUSION: In clinical practice, perfusion MRI could replace MET-PET for differentiating necrosis from tumour recurrence

[Identification of variables associated with time of hospital presentation after ischemic stroke: study of a rural population.]

We studied the time of arrival of 235 consecutive patients admitted to the emergency department of a University Hospital located in a rural area after the first symptoms of ischemic stroke or TIA. Among the following factors, we determined those that might be involved in delayed admission: place of symptom onset, time and place of onset of the first symptoms, contact with a general practitioner before admission time, mode of transportation, clinical score, impairment of consciousness, presence of seizures, heart complaints or headache, age and past medical history of cerebrovascular, cardiovascular and hypertension diseases. Half of the patients arrived within 4 h 10 of symptom discovery and 55 p. cent arrived within 6 hours. The percentage of patients arriving within 3h (p=0.001) and 6 h (p=0.001) was higher for those who had a stroke during the day (8 a.m.-8 p.m) than during the evening and night. The other characteristics associated with a shorter delay included a low neurological score on the Mathew's Stroke Scale (p<0.001 at 3h and p=0.001 at 6h) and younger age (p=0.015 at 3h). Presence of headache delayed admission (p=0.010). Forty-five percent of patients arrive at the hospital 6 hours after the discovery of symptoms, too late to receive optimal stroke therapy. Widespread public education on stroke is necessary to reduce the delay of admission, particularly for old patients and in case of mild to moderate deficits

Dosage rapide des D-dimères (Biosite R) dans la prise en charge des maladies thromboemboliques veineuses en salle d'urgence

info:eu-repo/semantics/publishe