Switching behavior of droplets crossing nodes on a fiber network.

Lately, curious structures have been erected in arid regions: they are large nets able to catch water from fog. Tiny droplets condense on the mesh and are collected on the bottom of it. This innovative technology is crucial to obtain drinkable water in these inhospitable areas. Many studies aim to understand the behavior of droplets trapped on this entanglement of fibers. However, the motion of a droplet sliding on a network of inclined fibers and encountering several crossings when going down remains an open question. Here, we look at the path chosen by such a drop and, especially, we analyze its behavior at the different nodes of the array. We show that droplets may change from one fiber to another one depending on the slope and the diameter of these fibers. We prove that we can force a droplet to follow a specific path simply by carefully designing the fiber mesh. These findings are expected to provide a very convenient way to manipulate small droplets in applications from microfluidics to fog harvesting.

Magnetoelastic instability in soft thin films.

Ferromagnetic particles are incorporated in a thin soft elastic matrix. A lamella, made of this smart material, is studied experimentally and modeled. We show herein that thin films can be actuated using an external magnetic field applied through the system. The system is found to be switchable since subcritical pitchfork bifurcation is discovered in the beam shape when the magnetic field orientation is modified. Strong magnetoelastic effects can be obtained depending on both field strength and orientation. Our results provide versatile ways to contribute to many applications from the microfabrication of actuators to soft robotics. As an example, we created a small synthetic octopus piloted by an external magnetic field.

Compound droplet manipulations on fiber arrays.

Recent works demonstrated that fiber arrays may constitute new means of designing open digital microfluidic systems. Various processes, such as droplet motion, fragmentation, trapping, release, mixing and encapsulation, may be achieved on fiber arrays. However, handling a large number of tiny droplets resulting from the mixing of several liquid components is required for developing microreactors, smart sensors or microemulsifying drugs. Here, we show that the manipulation of tiny droplets onto fiber networks allows for creating compound droplets with a high complexity level. Moreover, this cost-effective and adjustable method may also be implemented with optical fibers in order to develop fluorescence-based biosensor.

Physical changes of amniotic membranes through glycerolization for the use as an epidermal substitute. Light and electron microscopic studies.

Our Department of Plastic and Reconstructive Surgery has routinely been using amnion preserved in glycerol for the treatment of debrided II degrees burns. This treatment is almost pain free and requires fewer changes of dressings and fewer anaesthetics. It also prevents overgrowing granulation tissue and lessens scarring.Since 1910 amnion has been used as biological wound dressing. Its advantages such as reduced loss of protein and electrolytes, fluids and energy as well as reducing the risk of infection and accelerated regeneration of the epithelium have been well documented in medical literature.In order to more closely examine the question of possible changes to the micro structure of the amnion through preservation and rehydration as well as the interaction between transplanted tissue and recipient, we have carried out several light and electron microscopic studies.Results showed that neither the treatment with glycerol, nor the pretransplantation rehydration eliminates the monolayer of surface epithelium of the amnion. Its complex architecture remains intact during the preservation process and is therefore suitable as a matrix for the growth of keratinocytes and thereby the healing process.In clinical use we found amnion to be an excellent wound dressing as it allows proper control of fluid, has sufficient permeability for gases, has good thermal properties, is impervious to micro-organisms and is free from toxic material.

Repair of the upper eyelid by means of the prepuce after severe burns.

Burns to the eyelid often constitute difficult problems for reconstruction or repair. Functional and aesthetic aspects have to be considered, and suitable donor sites are not readily available in severely burned patients. In male patients, the prepuce yields an almost ideal skin for eyelid repair because of its high elasticity and adequate texture. Two patients with repair of both upper eyelids using the prepuce are demonstrated. The color match of this skin graft is satisfying. If both layers of the prepuce are transplanted, they yield enough tissue to cover both upper eyelids. This method seems to be an adequate method of reconstruction of burned eyelids in severely burned male patients when the usual donor sites for skin grafts are not available.

[Problems with the seat belt]. / Zur Problematik des Sicherheitsgurtes.

The greater number of auto-accident victims treated during the observation period had not been using seat belts. Injuries characteristic of belt-usage were also noted. Although there was no significant difference between the two groups in number of injuries, the unbuckled passengers were consistently more seriously injured. In contrast to other studies, fractures of the extremities were more common in the unprotected group. Serious head injuries and head injuries on the whole were more numerous when seat belts were not fastened. The front and rear seat passengers without belts were found to be equally endangered.

[Observations on the behaviour of coxiella burneti in the argasid tick ornithodoros moubata (author's transl)]. / Beobachtungen über das Verhalten des Q-Fieber-Erregers (Coxiella burneti) in der Lederzecke Ornithodoros moubata

Based on a long-term study of many years, a report is given on the behaviour of Coxiella burneti in the argasid tick, Ornithodoros moubata. Recent observations were made on ticks infected on mice and subsequently maintained separately. Particular emphasis was placed upon the localization of the ricksettsiae in certain organs of the ticks, its excretion -also with regard to routes of transmission - and transovarial passage. C. burneti invade primarily the gut epithelial cells of the tick and these cells remain infested with the causative agent throughout the entire life of the vector. After a certain infection period, other organs of the tick may become also infected. Thus, infection of the coxal organ, of salivary glands, rectal ampullae and ovaries has been confirmed through the presence of the rickettsiae in the coxal fluid, saliva and excreta or through transovarial passage of the agent with the saliva during feeding transmission to a new host takes place. Infection of the various organs of the tick and excretion or passage of the agent is not necessarily the rule, but may be even considered as an exception. This is especially the case for transovarial passage. On the other side, the multiplication of rickettsiae in the tick can be so intensive that the haemolymph and all internal organs become flooded with the organisms. These observations have been made in moribund and dead ticks. One of the most remarkable results was that the behaviour of C. burneti in its tick host varied considerably not only within the same series of experiments but more frequently in one and the same individual tick as well. Thus, e.g. excretion of the agent - with the saliva or coxal fluid - could be interrupted and resumed again later on. Evidently, these variations indicate a shift in the host-parasite interrelationship in which the multiplication of the rickettsiae is greatly enhanced by a decrease in the host's immune response, whereas an increase in its defence reaction will cause suppression of multiplication. It is not known, however, if the relevant impulse is primarily given by the tick or the rickettsial organism. The behaviour of C. burneti in O. moubata which does not follow a definite pattern coincides well with the high adaptability and variability characterizing this microorganism in other aspects as well.