Fluctations and noise in time-resolved light scattering experiments : measuring temporally heterogeneous dynamics

We use Time Resolved Correlation (TRC), a recently introduced light scattering method, to study the dynamics of a variety of jammed, or glassy, soft materials. The output of a TRC experiment is cI(t,tau), the time series of the degree of correlation between the speckle patterns generated by the light scattered at time t and t+tau. We characterize the fluctuations of cI by calculating their Probability Density Function, their variance as a function of the lag tau, and their time autocorrelation function. The comparison between these quantities for a Brownian sample and for jammed materials indicate unambiguously that the slow dynamics measured in soft glasses is temporally heterogeneous. The analogies with recent experimental, numerical and theoretical work on temporal heterogeneity in the glassy dynamics are briefly discussed.Comment: date de la fin de redaction : 06/09/200

Spatial-Temporal Graph Attention Fuser for Calibration in IoT Air Pollution Monitoring Systems

The use of Internet of Things (IoT) sensors for air pollution monitoring has significantly increased, resulting in the deployment of low-cost sensors. Despite this advancement, accurately calibrating these sensors in uncontrolled environmental conditions remains a challenge. To address this, we propose a novel approach that leverages graph neural networks, specifically the graph attention network module, to enhance the calibration process by fusing data from sensor arrays. Through our experiments, we demonstrate the effectiveness of our approach in significantly improving the calibration accuracy of sensors in IoT air pollution monitoring platforms

Time Resolved Correlation measurements of temporally heterogeneous dynamics

Time Resolved Correlation (TRC) is a recently introduced light scattering technique that allows to detect and quantify dynamic heterogeneities. The technique is based on the analysis of the temporal evolution of the speckle pattern generated by the light scattered by a sample, which is quantified by $c\_I(t,\tau)$, the degree of correlation between speckle images recorded at time $t$ and $t+\tau$. Heterogeneous dynamics results in significant fluctuations of $c\_I(t,\tau)$ with time $t$. We describe how to optimize TRC measurements and how to detect and avoid possible artifacts. The statistical properties of the fluctuations of $c\_I$ are analyzed by studying their variance, probability distribution function, and time autocorrelation function. We show that these quantities are affected by a noise contribution due to the finite number $N$ of detected speckles. We propose and demonstrate a method to correct for the noise contribution, based on a $N\to \infty$ extrapolation scheme. Examples from both homogeneous and heterogeneous dynamics are provided. Connections with recent numerical and analytical works on heterogeneous glassy dynamics are briefly discussed.Comment: 19 pages, 15 figures. Submitted to PR

Calibration of insulin pumps based on discrete doses at given cycle times

Funding Information: Research funding: This project 18HLT08 MEDDII has received funding from the EMPIR programme co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme. Publisher Copyright: © 2022 the author(s), published by De Gruyter, Berlin/Boston.One application in the medical treatment at very small flow rates is the usage of an Insulin pump that delivers doses of insulin at constant cycle times for a specific basal rate as quasi-continuous insulin delivery, which is an important cornerstone in diabetes management. The calibration of these basal rates are performed by either gravimetric or optical methods, which have been developed within the European Metrology Program for Innovation and Research (EMPIR) Joint Research Project (JRP) 18HLT08 Metrology for drug delivery II (MeDDII). These measurement techniques are described in this paper, and an improved approach of the analytical procedure given in the standard IEC 60601-2-24:2012 for determining the discrete doses and the corresponding basal rates is discussed in detail. These improvements allow detailed follow up of dose cycle time and delivered doses as a function of time to identify some artefacts of the measurement method or malfunctioning of the insulin pump. Moreover, the calibration results of different basal rates and bolus deliveries for the gravimetric and the optical methods are also presented. Some analysis issues that should be addressed to prevent misinterpreting of the calibration results are discussed. One of the main issues is the average over a period of time which is an integer multiple of the cycle time to determine the basal rate with the analytical methods described in this paper.publishersversionpublishe

Unexpected spatial distribution of bubble rearrangements in coarsening foams

Foams are ideal model systems to study stress-driven dynamics, as stress-imbalances within the system are continuously generated by the coarsening process, which unlike thermal fluctuations, can be conveniently quantified by optical means. However, the high turbidity of foams generally hinders the detailed study of the temporal and spatial distribution of rearrangement events, such that definite assessments regarding their contribution to the overall dynamics could not be made so far. In this paper, we use novel light scattering techniques to measure the frequency and position of events within a large sample volume. As recently reported (A. S. Gittings and D. J. Durian, Phys. Rev. E, 2008, 78, 066313), we find that the foam dynamics is determined by two distinct processes: intermittent bubble rearrangements of finite duration and a spatially homogeneous quasicontinuous process. Our experiments show that the convolution of these two processes determines the age-dependence of the mean dynamics, such that relations between intermittent rearrangements and coarsening process can not be established by considering means. By contrast the use of the recently introduced photon correlation imaging technique (A. Duri, D. A. Sessoms, V. Trappe, and L. Cipelletti, Phys. Rev. Lett., 2009, 102, 085702) enables us to assess that the event frequency is directly determined by the strain-rate imposed by the coarsening process. Surprisingly, we also find that, although the distribution of successive events in time is consistent with a random process, the spatial distribution of successive events is not random: rearrangements are more likely to occur within a recently rearranged zone. This implies that a topological rearrangement is likely to lead to an unstable configuration, such that a small amount of coarsening-induced strain is sufficient to trigger another event

Assessment of drug delivery devices working at microflow rates

Funding Information: Research funding: This work performed under the 18HLT08 MeDD II project has received funding from the EMPIR program co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation program. For more information on the project refer to the website www.drugmetrology.com . Publisher Copyright: © 2022 the author(s), published by De Gruyter, Berlin/Boston.Almost every medical department in hospitals around the world uses infusion devices to administer fluids, nutrition, and medications to patients to treat many different diseases and ailments. There have been several reports on adverse incidents caused by medication errors associated with infusion equipment. Such errors can result from malfunction or improper use, or even inaccuracy of the equipment, and can cause harm to patients' health. Depending on the intended use of the equipment, e.g. if it is used for anaesthesia of adults or for medical treatment of premature infants, the accuracy of the equipment may be more or less important. A well-defined metrological infrastructure can help to ensure that infusion devices function properly and are as accurate as needed for their use. However, establishing a metrological infrastructure requires adequate knowledge of the performance of infusion devices in use. This paper presents the results of various tests conducted with two types of devices.publishersversionpublishe

Calibration of insulin pumps based on discrete doses at given cycle times

One application in the medical treatment at very small flow rates is the usage of an Insulin pump that delivers doses of insulin at constant cycle times for a specific basal rate as quasi-continuous insulin delivery, which is an important cornerstone in diabetes management. The calibration of these basal rates are performed by either gravimetric or optical methods, which have been developed within the European Metrology Program for Innovation and Research (EMPIR) Joint Research Project (JRP) 18HLT08 Metrology for drug delivery II (MeDDII). These measurement techniques are described in this paper, and an improved approach of the analytical procedure given in the standard IEC 60601-2-24:2012 for determining the discrete doses and the corresponding basal rates is discussed in detail. These improvements allow detailed follow up of dose cycle time and delivered doses as a function of time to identify some artefacts of the measurement method or malfunctioning of the insulin pump. Moreover, the calibration results of different basal rates and bolus deliveries for the gravimetric and the optical methods are also presented. Some analysis issues that should be addressed to prevent misinterpreting of the calibration results are discussed. One of the main issues is the average over a period of time which is an integer multiple of the cycle time to determine the basal rate with the analytical methods described in this paper

Improving Process Quality by Means of Accurate and Traceable Calibration of Flow Devices with Process-oriented Liquids

Calibration of flow devices is important in several areas of pharmaceutical, flow chemistry and health care applications where volumetric dosage or delivery at given flow rates are crucial for the process. Although most of the flow devices are measuring flow rates of process-oriented liquids, their calibrations are often performed with water as calibration liquid. It is recommended to perform the calibrations of the flow devices with process-oriented liquids as the liquid itself might influence the performance of the flow devices. Therefore, METAS has developed facilities with METAS flow generators to address the issue of measuring with process-oriented liquids for flow rates from 400 ml/min down to 50 nl/min with uncertainties from 0.07–0.9 %. Traceability is guaranteed through the calibration of the generated flow rates of the METAS flow generators by means of the dynamic gravimetric method where a liquid of well-known density and a well-controlled evaporation rate is used. The design of the milli-flow facility will be discussed as well as first measurement results of the METAS flow generators in the range of micro-flow and milli-flow using water and other liquids