Rotifer niche segregation factors

The niche space of a species has been defined as the region in N-dimensional environmental hyperspace in which the fitness of the individuals is positive. In zooplankton assemblages, there has been little consideration of how different density-dependent (i.e. resources) and density-independent (i.e. conditions) environmental factors relate to fitness components in the field, namely survival and reproduction. We studied the abundance and reproduction (egg ratio) variability of seven species of pelagic rotifers living in a high-mountain lake and their relation to a number of environmental factors by means of partial canonical correspondence analyses. The generally higher explanatory capacity of conditions over resources suggests that habitat partitioning among species largely relies on historical processes, which are internalised in life history traits of spatial and temporal habitat use. However, the increase in the relevance of resources when considering reproduction, as compared to abundance, indicates that there is still an on-going interactive niche segregation process among rotifer species, which affects present and future rotifer assemblages in the lake. Our study shows the value of considering measurements close to fitness components (e.g. egg ratio) for detecting on-going niche segregation processes in zooplankton, which may help to resolve paradoxes in relation to species coexistence in natural assemblages.Peer reviewe

Axlebox accelerations: Their acquisition and time frequency characterisation for railway track monitoring purposes

[EN] Railway track maintenance is becoming a real challenge for Railway Engineers due to the need of meeting increasingly high quality requirements by means of cost-effective procedures. Frequently, this can be only achieved by implementing some technological developments from other fields into the railway sector, such as Digital Signal Processing. Indeed, the present work delves into data acquisition and processing techniques in order to enhance track surveying processes. For this purpose, run tests on the Metropolitan Rail Network of Valencia (Spain) were carried out, and axlebox accelerations were gathered and analysed in different ways. The results determined the optimal sampling and filtering frequencies as well as the location of accelerometers along the train. Furthermore, by means of spectral analysis and time frequency representations, diverse track defects, track singularities and vibration modes can be clearly identified. It is shown how, with a Hamming time window of 0.5 s and an overlapping of 95%, a wide set of track defects can be detected, without the need of complementary analyses. These values yield the best results as they are a good compromise between time and frequency resolution and allow for appropriate pattern recognition of the corresponding track singularities and resonant frequencies.Project Funded by Geoconcept Co. Ltd. and the Spanish Ministry of Economy and Competitiveness. Ref. IDI-20110461.Salvador Zuriaga, P.; Naranjo Ornedo, V.; Insa Franco, R.; Teixeira, P. (2016). Axlebox accelerations: Their acquisition and time frequency characterisation for railway track monitoring purposes. Measurement. 82:301-312. doi:10.1016/j.measurement.2016.01.012S3013128

Adaptive noise cancelling and time–frequency techniques for rail surface defect detection

Adaptive noise cancelling (ANC) is a technique which is very effective to remove additive noises from the contaminated signals. It has been widely used in the fields of telecommunication, radar and sonar signal processing. However it was seldom used for the surveillance and diagnosis of mechanical systems before late of 1990s. As a promising technique it has gradually been exploited for the purpose of condition monitoring and fault diagnosis. Time-frequency analysis is another useful tool for condition monitoring and fault diagnosis purpose as time-frequency analysis can keep both time and frequency information simultaneously. This paper presents an ANC and time-frequency application for railway wheel flat and rail surface defect detection. The experimental results from a scaled roller test rig show that this approach can significantly reduce unwanted interferences and extract the weak signals from strong background noises. The combination of ANC and time-frequency analysis may provide us one of useful tools for condition monitoring and fault diagnosis of railway vehicles

Verification of the use of micro-CT scanning to assess the features of entire squat type defects

Squats and studs are defects in railheads that share features, but have different causes. This paper examined four squat and stud samples from three different traffic environments to compare features using μ-CT X-ray scans, surface and subsurface inspection. μ-CT scanning has been used before as a non-destructive method to investigate rail defects, but not the entire defect. The scans were verified and allowed the identification of areas of interest when sectioning the samples further. The scan volumes were also used to create 3D models of the crack networks for the 3 samples that were scanned. All defects contain similar superficial features but the depth and severity of the subsurface damage varies. This work provides a visualisation of the 3D nature of studs in a way not seen before, as a 3D model the crack network from an in-service defect. The models of two of the defects showed the influence of hollow wheels initiating defects, as the crack seemed to initiate on the field side, grow down and towards the gauge side, before resurfacing as the longitudinal crack noted in all four defect samples. One sample is believed to have initiated due to contamination of the weld and the only squat sample, which failed in track, was believed to be ingot cast steel containing many inclusions. Three samples were studs and one was a squat. Each defect developed for different reasons, although the two metro samples were similar. One of the studs shows branching of cracks that, based on its changing angle of growth, could continue to grow into transverse defects, breaking the rail. The three defects that were scanned would all be classed as studs, but their crack morphology varies, possibly because they are all from different traffic environments. They also show slight differences to other studs in literature

Treatment of toxic hepatitis in COVID-19 patients

Background. The article reflects the clinical significance of the early diagnosis of toxic hepatitis in patients who have undergone a new coronavirus infection with the determination of clinical and laboratory predictors of the response to therapy. A dynamic analysis of the effectiveness of toxic hepatitis therapy in patients of three experimental groups and a control group is presented. Aim. The aim of the present study is to increase the effectiveness of the treatment of toxic hepatitis in patients who have undergone COVID-19. Materials and methods. On the basis of the newly created infection centers of the Central Clinical Hospital RZhD-Medicine and Vishnevsky 3-rd Central Military Clinical Hospital 996 patients with COVID-19, who had clinical and laboratory signs of toxic liver damage (cytolytic and/or cholestatic syndromes) against the background of COVID-19 therapy. Results. On the 14th day from the start of therapy in group 3, there was a significant decrease in the clinical manifestations of jaundice in 163 (72.8%) patients, on the 21st day of treatment, this symptom was stopped in all patients. In groups 1 and 2, the decrease in clinical manifestations of jaundice was significantly lower 122 (55.2%) and 134 (58.8%); p0.05. At the end of therapy, no manifestations of jaundice were observed in all experimental groups, while in the control group, symptom reduction was achieved only in 47 (14.5%) patients. Conclusion. The use of drugs with hepatoprotective effect in the form of monotherapy in groups 1 (UDCA) and 2 (ademethionine) showed a low therapeutic effect with positive dynamics of clinical and laboratory indicators of toxic hepatitis activity. The use of combined treatment in group 3 (UDCA and ademethionine) demonstrated the maximum therapeutic effect, pronounced positive dynamics in the form of normalization of clinical and laboratory indicators of toxic hepatitis activity