Confined cavitation : an experimental study

The behavior of a cavitation bubble is greatly influenced by its surroundings.\ud In an unbounded liquid a cavitation bubble grows and collapses\ud spherically but a nearby solid boundary changes everything. Now the\ud bubble collapses towards the wall and looses its spherical shape. During\ud collapse a thin jet is formed piercing through the center of the bubble\ud aimed towards the wall. Upon impacting on the boundary the jet spreads\ud out radially exerting a strong shear stress on the wall. The shear strength\ud drops with a -11=4 power law.\ud The strength of the jet depends strongly on the starting distance between\ud the bubble and the wall. The jet impact velocity increases the closer\ud the bubble gets to the wall up to a maximum for a standoff distance of\ud about » 0.6. For bubbles closer than that the jet velocity decreases.\ud This jet flow can be utilized to temporarily porate the membranes of\ud living cells; adherent cells are grown on the wall of a culture flask and exposed\ud to a single cavitation bubble. As the jet impacts on the cell monolayer\ud it detaches cells in a circular region around the point of impact. Surrounding\ud the cleared area there is a ring where the shear stress was to\ud weak to detach the cells but strong enough to rip small holes in the cell\ud membrane.\ud This permeabilization of the membrane can be detected by adding a\ud dye to the liquid such that only the porated cells will be stained. Afterwards\ud the cells are tracked for an entire day to make sure they survive the\ud treatment.\ud Interestingly enough when a bubble is created with a standoff distance\ud smaller than ° = 0.6 the amount of stained cells keeps increasing while\ud the circular detachment area shrinks. The cause for this is the bubble\ud growth on top off the surface which is also strong enough to porate cells.\ud This finding can be used for instance in microfluidics. If a bubble is\ud created in a thin liquid film between two parallel plates the bubble takes\ud on a flat pancake like shape. This quasi 2-dimensional bubble grows and\ud collapses in a circular fashion and no jets are formed. But as was shown before bubble growth across a surface can also porate cells and by growing\ud cells on one of the two walls in such a system this was also proven the case\ud in microfluidics.\ud Cells in suspension can also be porated but during bubble growth they\ud take on a ”tear” shape which is expected to be a result of entraining the\ud cell from the boundary layer into the main flow. A way to circumvent this\ud instability we created a second bubble on the other side of the cell. The\ud cell becomes compressed and simultaneously sheared yet it remains in\ud place.\ud Bubbles in confined geometries jet in the presence of a channel wall;\ud even when a small channel opening is present. By positioning the bubble\ud such that the jet does not impact on the wall but flows into the a channel\ud opening realizes a pump. This idea which was put forward for larger millimeter\ud sized bubbles by Khoo’s group (Khoo, et.al. 2005) has now been\ud for the first time realized on the microscale for lab on a chip devices.\ud Similar to the step from 3D to 2D the addition of second side wall\ud close the first side wall takes us from 2D to a quasi 1-dimensional bubble.\ud A bubble generated in such a long and thin channel only grows and\ud collapses in the lengthwise direction of the channel. A one dimensional\ud model does indeed describe the bubble dynamics quite accurately but\ud only if the temperature inside the bubble is taken into account.\ud This time another solid boundary will not induce jetting in the bubble.\ud A free interface close to the jet however does result in a jet. It is however\ud not a jet penetrating through the bubble but the result of the rapidly growing\ud bubble pushing liquid out of the open end of the channel. We demonstrate\ud on demand and reproducible jetting on the micrometer scale with\ud more than 100 m/s

The impact of regionalized trauma care on the distribution of severely injured patients in the Netherlands

BACKGROUND: Twenty years ago, an inclusive trauma system was implemented in the Netherlands. The goal of this study was to evaluate the impact of structured trauma care on the concentration of severely injured patients over time. METHODS: All severely injured patients (Injury Severity Score [ISS] ≥ 16) documented in the Dutch Trauma Registry (DTR) in the calendar period 2008–2018 were included for analysis. We compared severely injured patients, with and without severe neurotrauma, directly brought to trauma centers (TC) and non-trauma centers (NTC). The proportion of patients being directly transported to a trauma center was determined, as was the total Abbreviated Injury Score (AIS), and ISS. RESULTS: The documented number of severely injured patients increased from 2350 in 2008 to 4694 in 2018. During this period, on average, 70% of these patients were directly admitted to a TC (range 63–74%). Patients without severe neurotrauma had a lower chance of being brought to a TC compared to those with severe neurotrauma. Patients directly presented to a TC were more severely injured, reflected by a higher total AIS and ISS, than those directly transported to a NTC. CONCLUSION: Since the introduction of a well-organized trauma system in the Netherlands, trauma care has become progressively centralized, with more severely injured patients being directly presented to a TC. However, still 30% of these patients is initially brought to a NTC. Future research should focus on improving pre-hospital triage to facilitate swift transfer of the right patient to the right hospital

Modulation of epithelial sodium channel (ENaC) expression in mouse lung infected with Pseudomonas aeruginosa

BACKGROUND: The intratracheal instillation of Pseudomonas aeruginosa entrapped in agar beads in the mouse lung leads to chronic lung infection in susceptible mouse strains. As the infection generates a strong inflammatory response with some lung edema, we tested if it could modulate the expression of genes involved in lung liquid clearance, such as the α, β and γ subunits of the epithelial sodium channel (ENaC) and the catalytic subunit of Na(+)-K(+)-ATPase. METHODS: Pseudomonas aeruginosa entrapped in agar beads were instilled in the lung of resistant (BalB/c) and susceptible (DBA/2, C57BL/6 and A/J) mouse strains. The mRNA expression of ENaC and Na(+)-K(+)-ATPase subunits was tested in the lung by Northern blot following a 3 hours to 14 days infection. RESULTS: The infection of the different mouse strains evoked regulation of α and β ENaC mRNA. Following Pseudomonas instillation, the expression of αENaC mRNA decreased to a median of 43% on days 3 and 7 after infection and was still decreased to a median of 45% 14 days after infection (p < 0.05). The relative expression of βENaC mRNA was transiently increased to a median of 241%, 24 h post-infection before decreasing to a median of 43% and 54% of control on days 3 and 7 post-infection (p < 0.05). No significant modulation of γENaC mRNA was detected although the general pattern of expression of the subunit was similar to α and β subunits. No modulation of α(1)Na(+)-K(+)-ATPase mRNA, the catalytic subunit of the sodium pump, was recorded. The distinctive expression profiles of the three subunits were not different, between the susceptible and resistant mouse strains. CONCLUSIONS: These results show that Pseudomonas infection, by modulating ENaC subunit expression, could influence edema formation and clearance in infected lungs

Safety Helmet 2.0: A brainstorm based approach

The Saxion University of Applied Sciences has recently started the project &ldquo;Safety at Work&rdquo;. The objective of the project is to increase safety at the workplace by applying and combining state of the art artifacts from the three disciplines: 1) Ambient Intelligence 2) Industrial &amp; Product Design and 3) Smart Functional Materials. One strong factor that influences safety is human behavior. In the areas of marketing- and neuropsychology there are many examples of influencing human behavior [1, 2]. Interviews [3] with project partners and literature [4&ndash;7], show that often industrial workers do not wear all the prescribed safety gear (safety helmets, safety goggles, etc.). An especially big problem for industrial environments is that many workers are not willing to wear helmets simply because they are not comfortable [4, 5], or they expect the dangers of not wearing one to be negligible. Acknowledging this problem, we decided to introduce factors of marketing- and neuropsychology to Industrial Design students. These students participated in a full day creative session in which they attended a master class about the concepts of marketing- and neuropsychology, participated in a brainstorm and developed concepts of products that influence safe behavior. This paper focuses on the process of the brainstorm and concept development, it also gives an overview on the final concepts that delivered