459 research outputs found

    Fish swimming in schools save energy regardless of their spatial position

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    For animals, being a member of a group provides various advantages, such as reduced vulnerability to predators, increased foraging opportunities and reduced energetic costs of locomotion. In moving groups such as fish schools, there are benefits of group membership for trailing individuals, who can reduce the cost of movement by exploiting the flow patterns generated by the individuals swimming ahead of them. However, whether positions relative to the closest neighbours (e.g. ahead, sided by side or behind) modulate the individual energetic cost of swimming is still unknown. Here, we addressed these questions in grey mullet Liza aurata by measuring tail-beat frequency and amplitude of 15 focal fish, swimming in separate schools, while swimming in isolation and in various positions relative to their closest neighbours, at three speeds. Our results demonstrate that, in a fish school, individuals in any position have reduced costs of swimming, compared to when they swim at the same speed but alone. Although fish swimming behind their neighbours save the most energy, even fish swimming ahead of their nearest neighbour were able to gain a net energetic benefit over swimming in isolation, including those swimming at the front of a school. Interestingly, this energetic saving was greatest at the lowest swimming speed measured in our study. Because any member of a school gains an energetic benefit compared to swimming alone, we suggest that the benefits of membership in moving groups may be more strongly linked to reducing the costs of locomotion than previously appreciated

    The association between socioeconomic position, use of revascularization procedures and five-year survival after recovery from acute myocardial infarction

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    Background: Patients living under better socioeconomic circumstances often receive more active treatments after an acute myocardial infarction (AMI) compared to less affluent patients. However, most previous studies were performed in countries with less comprehensive coverage for medical services. In this Swedish nation-wide longitudinal study we wanted to evaluate long-term survival after AMI in relation to socioeconomic position (SEP) and use of revascularization. Methods: From the Swedish Myocardial Infarction Register we identified all 45 to 84-year-old patients (16,041 women and 30,366 men) alive 28 days after their first AMI during the period 1993 to 1996. We obtained detailed information on the use of revascularization, cumulative household income from the 1975 and 1990 censuses and 5-year survival after the AMI. Results: Patients with the highest cumulative income (adding the values of the quartile categories of income in 1975 and 1990) underwent a revascularization procedure within one month after their first AMI two to three times as often as patients with the lowest cumulative income and had half the risk of death within five years. The socioeconomic differences in the use of revascularization procedures could not be explained by differences in co-morbidity or type of hospital at first admission. Patients who underwent revascularization showed a similar lowered mortality risk in the different income groups, while there were strong socioeconomic differences in long-term mortality among patients who did not undergo revascularization. Conclusion: This nationwide Swedish study showed that patients with high income had a better long-term survival after recovery from their AMI compared to patients with low income. Furthermore, even though the use of revascularization procedures is beneficial, low SEP groups receive it less often than high SEP groups.Maria Rosvall, Basile Chaix, John Lynch, Martin Lindström, and Juan Merl

    Similar support for three different life course socioeconomic models on predicting premature cardiovascular mortality and all-cause mortality

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    BACKGROUND: There are at least three broad conceptual models for the impact of the social environment on adult disease: the critical period, social mobility, and cumulative life course models. Several studies have shown an association between each of these models and mortality. However, few studies have investigated the importance of the different models within the same setting and none has been performed in samples of the whole population. The purpose of the present study was to study the relation between socioeconomic position (SEP) and mortality using different conceptual models in the whole population of Scania. METHODS: In the present investigation we use socioeconomic information on all men (N = 48,909) and women (N = 47,688) born between 1945 and 1950, alive on January, 1(st),1990, and living in the Region of Scania, in Sweden. Focusing on three specific life periods (i.e., ages 10–15, 30–35 and 40–45), we examined the association between SEP and the 12-year risk of premature cardiovascular mortality and all-cause mortality. RESULTS: There was a strong relation between SEP and mortality among those inside the workforce, irrespective of the conceptual model used. There was a clear upward trend in the mortality hazard rate ratios (HRR) with accumulated exposure to manual SEP in both men (p for trend < 0.001 for both cardiovascular and all-cause mortality) and women (p for trend = 0.01 for cardiovascular mortality) and (p for trend = 0.003 for all-cause mortality). Inter- and intragenerational downward social mobility was associated with an increased mortality risk. When applying similar conceptual models based on workforce participation, it was shown that mortality was affected by the accumulated exposure to being outside the workforce. CONCLUSION: There was a strong relation between SEP and cardiovascular and all-cause mortality, irrespective of the conceptual model used. The critical period, social mobility, and cumulative life course models, showed the same fit to the data. That is, one model could not be pointed out as "the best" model and even in this large unselected sample it was not possible to adjudicate which theories best describe the links between life course SEP and mortality risk

    Species distributions models may predict accurately future distributions but poorly how distributions change : A critical perspective on model validation

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    Aim: Species distribution models (SDMs) are widely used to make predictions on how species distributions may change as a response to climatic change. To assess the reliability of those predictions, they need to be critically validated with respect to what they are used for. While ecologists are typically interested in how and where distributions will change, we argue that SDMs have seldom been evaluated in terms of their capacity to predict such change. Instead, typical retrospective validation methods estimate model's ability to predict to only one static time in future. Here, we apply two validation methods, one that predicts and evaluates a static pattern, while the other measures change and compare their estimates of predictive performance. Location: Fennoscandia.Methods: We applied a joint SDM to model the distributions of 120 bird species in four model validation settings. We trained models with a dataset from 1975 to 1999 and predicted species' future occurrence and abundance in two ways: for one static time period (2013- 2016, "static validation') and for a change between two time periods (difference between 1996- 1999 and 2013- 2016, "change validation'). We then measured predictive performance using correlation between predicted and observed values. We also related predictive performance to species traits. Results: Even though static validation method evaluated predictive performance as good, change method indicated very poor performance. Predictive performance was not strongly related to any trait.Main Conclusions: Static validation method might overestimate predictive performance by not revealing the model's inability to predict change events. If species' distributions remain mostly stable, then even an unfit model can predict the near future well due to temporal autocorrelation. We urge caution when working with forecasts of changes in spatial patterns of species occupancy or abundance, even for SDMs that are based on time series datasets unless they are critically validated for forecasting such change.Peer reviewe

    Ротаційно–ударна обробка спіралей шнеків

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    Forskningsinriktningen vid den historiska avdelningen vid Linköpings universitet har sedan länge en stark socialhistorisk profil. kollektivens vardag studeras på en rad områden, på olika nivåer och över sinsemellan skilda tidsperioder. Det gäller inom såväl agrara som industriella miljöer, på samhällelig liksom på grupp-, familje- och individnivå samt över tid som omspänner senantiken till det sena 1900-talets historia. Hur identiteter skapas, tillägnas och förändras är en alltmer växande inriktning, liksom anknytningen till socialpolitiska ideer, normsystem, attityder, värderingar och mentaliteter. Även den  rättshistoriska och ekonomiskhistoriska forskningen ryms inom detta fält. Den historiska demografin utgör också traditionellt en stark del av det socialhistoriska fältet. Studier av arbeta och ohälsa, sjuklighet, dödlighet och hälsopolitik ligger långt framme. Bredden i den socialhistoriska profilen morsvaras av en mångfald melodologiska inslag. Skriftserien Socialhistoria i Linköping uppmärksammar denna profil och vilka uttryck den tar sig i grundutbildningen. I serien publiceras i första hand uppsatser skrivna på C- och D- nivå, men även bidrag från lärare och doktorander vid avdelningen förekommer. Detta nummer av Socialhistoria i Linköping är en specialutgåva till Svenska historikermötet i Linköping 23-25 april 199

    On-board Clutch Slippage Detection and Diagnosis in Heavy Duty Machine

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    In order to reduce unnecessary stops and expensive downtime originating from clutch failure of construction equipment machines; adequate real time sensor data measured on the machine in combination with feature extraction and classification methods may be utilized. This paper presents a framework with feature extraction methods and an anomaly detection module combined with Case-Based Reasoning (CBR) for on-board clutch slippage detection and diagnosis in heavy duty equipment. The feature extraction methods used are Moving Average Square Value Filtering (MASVF) and a measure of the fourth order statistical properties of the signals implemented as continuous queries over data streams. The anomaly detection module has two components, the Gaussian Mixture Model (GMM) and the Logistics Regression classifier. CBR is a learning approach that classifies faults by creating a new solution for a new fault case from the solution of the previous fault cases. Through use of a data stream management system and continuous queries (CQs), the anomaly detection module continuously waits for a clutch slippage event detected by the feature extraction methods, the query returns a set of features, which activates the anomaly detection module. The first component of the anomaly detection module trains a GMM to extracted features while the second component uses a Logistic Regression classifier for classifying normal and anomalous data. When an anomaly is detected, the Case-Based diagnosis module is activated for fault severity estimation
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