173 research outputs found

    Quasi-cycles in a spatial predator-prey model

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    We show that spatial models of simple predator-prey interactions predict that predator and prey numbers oscillate in time and space. These oscillations are not seen in the deterministic versions of the models, but are due to stochastic fluctuations about the time-independent solutions of the deterministic equations which are amplified due to the existence of a resonance. We calculate the power spectra of the fluctuations analytically and show that they agree well with results obtained from stochastic simulations. This work extends the analysis of these quasi-cycles from that previously developed for well-mixed systems to spatial systems, and shows that the ideas and methods used for non-spatial models naturally generalize to the spatial case.Comment: 18 pages, 4 figure

    Personal body ornamentation on the Southern Iberian Meseta: An archaeomineralogical study

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    Beads and pendants from the Castillejo del Bonete (Terrinches, Ciudad Real) and Cerro Ortega (Villanueva de la Fuente, Ciudad Real) burials were analysed using XRD, micro-Raman and XRF in order to contribute to the current distribution map of green bead body ornament pieces on the Iberian Peninsula which, so far, remain undetailed for many regions. XRD, micro-Raman and XRF analyses showed that most of the beads from Castillejo del Bonete (Late 3rd millennium cal. BC) were made from variscite or green phyllosilicates, while Cerro Ortega's (Late 4th millenniumcal. BC) beads were made out of fossil wood or Clinochlore. Significantly enough,while XRD pointed to variscite as the main crystallo-graphic phase, the elemental composition did not match any elemental compositions of known and characterised sources, thus suggesting an unknown south-eastern source or an extra-peninsular origin of these ornamental pieces

    Comprehensive management of obstructive sleep apnea by telemedicine: Clinical improvement and cost-effectiveness of a Virtual Sleep Unit. A randomized controlled trial

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    Introduction: Obstructive sleep apnea (OSA) is a prevalent disease associated with significant morbidity and high healthcare costs. Information and communication technology could offer cost-effective management options. Objectives: To evaluate an out-of-hospital Virtual Sleep Unit (VSU) based on telemedicine to manage all patients with suspected OSA, including those with and without continuous positive airway pressure (CPAP) therapy.Methods: This was an open randomized controlled trial. Patients with suspected OSA were randomized to hospital routine (HR) or VSU groups to compare the clinical improvement and cost-effectiveness in a non-inferiority analysis. Improvement was assessed by changes in the Quebec Sleep Questionnaire (QSQ), EuroQol (EQ-5D and EQ-VAS), and Epworth Sleepiness Scale (ESS). The follow-up was 3 months. Cost-effectiveness was assessed by a Bayesian analysis based on quality-adjusted life-years (QALYs).Results: The HR group (n: 92; 78% OSA, 57% CPAP) compared with the VSU group (n: 94; 83% OSA, 43% CPAP) showed: CPAP compliance was similar in both groups, the QSQ social interactions domain improved significantly more in the HR group whereas the EQ-VAS improved more in the VSU group. Total and OSA-related costs were lower in the VSU group than the HR. The Bayesian cost-effectiveness analysis showed that VSU was cost-effective for a wide range of willingness to pay for QALYs. Conclusions: The VSU offered a cost-effective means of improving QALYs than HR. However, the assessment of its clinical improvement was influenced by the choice of the questionnaire; hence, additional measurements of clinical improvement are needed. Our findings indicate that VSU could help with the management of many patients, irrespective of CPAP use

    ATLAS Beam Steering Mechanism (BSM) Lessons Learned

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    This paper describes the design, testing, and lessons learned during the development of the Advanced Topographic Laser Altimeter System (ATLAS) Beam Steering Mechanism (BSM). The BSM is a 2 degree-of-freedom tip-tilt mechanism for the purpose of pointing a flat mirror to tightly control the co-alignment of the transmitted laser and the receiver telescope of the ATLAS instrument. The high resolution needs of the mission resulted in sub-arcsecond pointing and knowledge requirements, which have been met. Development of the methodology to verify performance required significant effort. The BSM will fly as part of the Ice, Cloud, and Elevation Satellite II Mission (ICESat II), which is scheduled to be launched in 2017. The ICESat II primary mission is to map the Earth's surface topography for the determination of seasonal changes of ice sheet thickness and vegetation canopy thickness to establish long-term trends

    Ciprofibrate therapy in patients with hypertriglyceridemia and low high density lipoprotein (HDL)-cholesterol: greater reduction of non-HDL cholesterol in subjects with excess body weight (The CIPROAMLAT study)

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    BACKGROUND: Hypertriglyceridemia in combination with low HDL cholesterol levels is a risk factor for cardiovascular disease. Our objective was to evaluate the efficacy of ciprofibrate for the treatment of this form of dyslipidemia and to identify factors associated with better treatment response. METHODS: Multicenter, international, open-label study. Four hundred and thirty seven patients were included. The plasma lipid levels at inclusion were fasting triglyceride concentrations between 1.6–3.9 mM/l and HDL cholesterol ≤ 1.05 mM/l for women and ≤ 0.9 mM/l for men. The LDL cholesterol was below 4.2 mM/l. All patients received ciprofibrate 100 mg/d. Efficacy and safety parameters were assessed at baseline and at the end of the treatment. The primary efficacy parameter of the study was percentage change in triglycerides from baseline. RESULTS: After 4 months, plasma triglyceride concentrations were decreased by 44% (p < 0.001). HDL cholesterol concentrations were increased by 10% (p < 0.001). Non-HDL cholesterol was decreased by 19%. A greater HDL cholesterol response was observed in lean patients (body mass index < 25 kg/m(2)) compared to the rest of the population (8.2 vs 19.7%, p < 0.001). In contrast, cases with excess body weight had a larger decrease in non-HDL cholesterol levels (-20.8 vs -10.8%, p < 0.001). There were no significant complications resulting from treatment with ciprofibrate. CONCLUSIONS: Ciprofibrate is efficacious for the correction of hypertriglyceridemia / low HDL cholesterol. A greater decrease in non-HDL cholesterol was found among cases with excess body weight. The mechanism of action of ciprofibrate may be influenced by the pathophysiology of the disorder being treated

    Peces de la cuenca del río Orinoco. Parte I: Lista de especies y distribución por subcuencas

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    Para efectos del presente trabajo y en función de los datos disponibles hasta la fecha, se consideran las siguientes subcuencas y/o regiones para la cuenca del Orinoco, desde su nacimiento hasta su desembocadura en el océano Atlántico: Alto Orinoco, Casiquiare, Ventuari, Atabapo, Inírida, Guaviare, Vichada, Sipapo, Tomo, Cataniapo, Bita, Meta, Parguaza, Cinaruco, Suapure, Capanaparo, Arauca, Apure, Cuchivero, Manapiare, Zuata, Caura, Pao, Aro, Caris, Caroní, Morichal Largo, Delta y Orinoco (Mapa)

    Phase III randomized trial of sunitinib versus capecitabine in patients with previously treated HER2-negative advanced breast cancer

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    This multicenter, randomized, open-label phase III trial (planned enrollment: 700 patients) was conducted to test the hypothesis that single-agent sunitinib improves progression-free survival (PFS) compared with capecitabine as treatment for advanced breast cancer (ABC). Patients with HER2-negative ABC that recurred after anthracycline and taxane therapy were randomized (1:1) to sunitinib 37.5 mg/day or capecitabine 1,250 mg/m2 (1,000 mg/m2 in patients >65 years) BID on days 1–14 q3w. The independent data-monitoring committee (DMC) determined during the first interim analysis (238 patients randomized to sunitinib, 244 to capecitabine) that the trial be terminated due to futility in reaching the primary endpoint. No statistical evidence supported the hypothesis that sunitinib improved PFS compared with capecitabine (one-sided P = 0.999). The data indicated that PFS was shorter with sunitinib than capecitabine (median 2.8 vs. 4.2 months, respectively; HR, 1.47; 95% CI, 1.16–1.87; two-sided P = 0.002). Median overall survival (15.3 vs. 24.6 months; HR, 1.17; two-sided P = 0.350) and objective response rates (11 vs. 16%; odds ratio, 0.65; P = 0.109) were numerically inferior with sunitinib versus capecitabine. While no new or unexpected safety findings were reported, sunitinib treatment was associated with higher frequencies and greater severities of many common adverse events (AEs) compared with capecitabine, resulting in more temporary discontinuations due to AEs with sunitinib (66 vs. 51%). The relative dose intensity was lower with sunitinib than capecitabine (73 vs. 95%). Based on these efficacy and safety results, sunitinib should not be used as monotherapy for patients with ABC

    Ancient dental calculus preserves signatures of biofilm succession and interindividual variation independent of dental pathology

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    Dental calculus preserves oral microbes, enabling comparative studies of the oral microbiome and health through time. However, small sample sizes and limited dental health metadata have hindered health-focused investigations to date. Here, we investigate the relationship between tobacco pipe smoking and dental calculus microbiomes. Dental calculus from 75 individuals fromthe 19th century Middenbeemster skeletal collection (Netherlands) were analyzed by metagenomics. Demographic and dental health parameters were systematically recorded, including the presence/number of pipe notches. Comparative data sets fromEuropean populations before and after the introduction of tobaccowere also analyzed. Calculus species profileswere comparedwith oral pathology to examine associations between microbiome community, smoking behavior, and oral health status. The Middenbeemster individuals exhibited relatively poor oral health,with a high prevalence of periodontal disease, caries, heavy calculus deposits, and antemortem tooth loss. No associations between pipe notches and dental pathologies, or microbial species composition,were found. Calculus samples before and after the introduction of tobacco showed highly similar species profiles. Observed interindividual microbiome differences were consistent with previously described variation in human populations from the Upper Paleolithic to the present. Dental calculus may not preserve microbial indicators of health and disease status as distinctly as dental plaque

    Beam Steering Mechanism (BSM) Lessons Learned

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    This paper describes the design, testing, and lessons learned during the development of the Advanced Topographic Laser Altimeter System (ATLAS) Beam Steering Mechanism (BSM). The BSM is a 2 degree-of-freedom tip-tilt mechanism for the purpose of pointing a flat mirror to tightly control the co-alignment of the transmitted laser and the receiver telescope of the ATLAS instrument. High resolution needs of the mission resulted in sub-arcsecond pointing and knowledge requirements, which have been met. Development of methodology to verify performance was a significant effortadvancement. The BSM will fly as part of the Ice, Cloud, and Elevation Satellite 2 Mission (ICESat 2), which is scheduled to be launched in 2017. The ICESat 2 primary mission is to map the earths surface topography for the determination of seasonal changes of ice sheet thickness as well as vegetation canopy thickness
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