The study of atmospheric ice-nucleating particles via microfluidically generated droplets

Ice-nucleating particles (INPs) play a significant role in the climate and hydrological cycle by triggering ice formation in supercooled clouds, thereby causing precipitation and affecting cloud lifetimes and their radiative properties. However, despite their importance, INP often comprise only 1 in 10³–10⁶ ambient particles, making it difficult to ascertain and predict their type, source, and concentration. The typical techniques for quantifying INP concentrations tend to be highly labour-intensive, suffer from poor time resolution, or are limited in sensitivity to low concentrations. Here, we present the application of microfluidic devices to the study of atmospheric INPs via the simple and rapid production of monodisperse droplets and their subsequent freezing on a cold stage. This device offers the potential for the testing of INP concentrations in aqueous samples with high sensitivity and high counting statistics. Various INPs were tested for validation of the platform, including mineral dust and biological species, with results compared to literature values. We also describe a methodology for sampling atmospheric aerosol in a manner that minimises sampling biases and which is compatible with the microfluidic device. We present results for INP concentrations in air sampled during two field campaigns: (1) from a rural location in the UK and (2) during the UK’s annual Bonfire Night festival. These initial results will provide a route for deployment of the microfluidic platform for the study and quantification of INPs in upcoming field campaigns around the globe, while providing a benchmark for future lab-on-a-chip-based INP studies

Sudden Cardiac Arrest due to Brugada Syndrome: a Case Report and Literature Review

Brugada Syndrome is a rare cause of sudden cardiac arrest and has a unique ECG pattern. In fact, with ST-segment elevation down sloping in the right precordial leads (v1-v3), RBBB pattern in lateral leads and J-point elevation is revealed. We must notice and avoid trigger factors of this syndrome during general anesthesia. Patient is a 39 old man who attended to emergency department with sudden cardiac arrest and resuscitate. He was transferred to ICU for management of hypoxic ischemic encephalopathy. Complementary studies concluded the diagnosis of Brugada syndrome. We must consider Brugada syndrome within patients with family history of sudden cardiac arrest. Moreover, we must avoid trigger factors of this syndrome such as fever, bradicardia and electrolyte abnormality (specialy Na, Ca abnormalities) during general anesthesia and if they appear, we should treat them

Lagrangian measurements of the fast evaporation of falling diethyl ether droplets using in-line digital holography and a high-speed camera

International audienceThe evaporation of falling diethyl ether droplets is measured by following droplets along their trajectories. Measurements are performed at ambient temperature and pressure by using in-line digital holography. The holograms of droplets are recorded with a single high-speed camera and reconstructed with an ''inverse problems'' approach algorithm previously tested (Chareyron et al. New J Phys 14:43039, 2012). Once evaporation starts, the interfaces of the droplets are surrounded by air/vapor mixtures with refractive index gradients that modify the holograms. The central part of the droplets holograms is unusually bright compared to what is expected and observed for non-evaporating droplets. The reconstruction process is accordingly adapted to measure the droplets diameter along their trajectory. The diethyl ether being volatile, the droplets are found to evaporate in a very short time: of the order of 70 ms for a 50-60 lm diameter at an ambient temperature of 25 C. After this time, the diethyl ether has fully evaporated and droplets diameter reaches a plateau. The remaining droplets are then only composed of water, originating from the cooling and condensation of the humid air at the droplet surface. This assertion is supported by two pieces of evidence: (i) by estimating the evolution of droplets refractive index from light scattering measurements at rainbow angle and (ii) by comparing the evaporation rate and droplets velocities obtained by digital holography with those calculated with a simple model of evaporation/condensation. The overall results show that the in-line digital holography with ''inverse problems''approach is an accurate technique for studying fast evaporation from a Lagrangian point of view