Swelling of two-dimensional polymer rings by trapped particles.

The mean area of a two-dimensional Gaussian ring of N monomers is known to diverge when the ring is subject to a critical pressure differential, p c ~ N -1. In a recent publication (Eur. Phys. J. E 19, 461 (2006)) we have shown that for an inextensible freely jointed ring this divergence turns into a second-order transition from a crumpled state, where the mean area scales as [A]~N-1, to a smooth state with [A]~N(2). In the current work we extend these two models to the case where the swelling of the ring is caused by trapped ideal-gas particles. The Gaussian model is solved exactly, and the freely jointed one is treated using a Flory argument, mean-field theory, and Monte Carlo simulations. For a fixed number Q of trapped particles the criticality disappears in both models through an unusual mechanism, arising from the absence of an area constraint. In the Gaussian case the ring swells to such a mean area, [A]~ NQ, that the pressure exerted by the particles is at p c for any Q. In the freely jointed model the mean area is such that the particle pressure is always higher than p c, and [A] consequently follows a single scaling law, [A]~N(2) f (Q/N), for any Q. By contrast, when the particles are in contact with a reservoir of fixed chemical potential, the criticality is retained. Thus, the two ensembles are manifestly inequivalent in these systems.

Microscopic folds and macroscopic jerks in compressed lipid monolayers.

We report hitherto unrecognized cooperative behavior in the stochastic collapse of certain compressed lipid monolayers implicated in pulmonary function. The cooperativity emerges from a statistical analysis of the collapse events captured using fluorescence microscopy and digital image analysis. The collapse events involve folding of the monolayer on a micron scale, yet each event produces a macroscopic jerk of the layer. The cooperative collapse is striking for its temporal sharpness and large spatial extent.

Smoothening transition of a two-dimensional pressurized polymer ring.

We revisit the problem of a two-dimensional polymer ring subject to an inflating pressure differential. The ring is modeled as a freely jointed closed chain of N monomers. Using a Flory argument, mean-field calculation and Monte Carlo simulations, we show that at a critical pressure, p(c) approximately N(-1), the ring undergoes a second-order phase transition from a crumpled, random-walk state, where its mean area scales as approximately N, to a smooth state with approximately N(2). The transition belongs to the mean-field universality class. At the critical point a new state of polymer statistics is found, in which approximately N(3/2). For p >> p(c) we use a transfer-matrix calculation to derive exact expressions for the properties of the smooth state.

Topography and instability of monolayers near domain boundaries.

We theoretically study the topography of a biphasic surfactant monolayer in the vicinity of domain boundaries. The differing elastic properties of the two phases generally lead to a nonflat topography of "mesas," where domains of one phase are elevated with respect to the other phase. The mesas are steep but low, having heights of up to 10 nm. As the monolayer is laterally compressed, the mesas develop overhangs and eventually become unstable at a surface tension of about K(deltac(0))(2) (deltac(0) being the difference in spontaneous curvature and K a bending modulus). In addition, the boundary is found to undergo a topography-induced rippling instability upon compression, if its line tension is smaller than about Kdeltac(0). The effect of diffuse boundaries on these features and the topographic behavior near a critical point are also examined. We discuss the relevance of our findings to several experimental observations related to surfactant monolayers: (i) small topographic features recently found near domain boundaries; (ii) folding behavior observed in mixed phospholipid monolayers and model lung surfactants; (iii) roughening of domain boundaries seen under lateral compression; (iv) the absence of biphasic structures in tensionless surfactant films.

Binding of molecules to DNA and other semiflexible polymers.

A theory is presented for the binding of small molecules such as surfactants to semiflexible polymers. The persistence length is assumed to be large compared to the monomer size but much smaller than the total chain length. Such polymers (e.g., DNA) represent an intermediate case between flexible polymers and stiff, rodlike ones, whose association with small molecules was previously studied. The chains are not flexible enough to actively participate in the self-assembly, yet their fluctuations induce long-range attractive interactions between bound molecules. In cases where the binding significantly affects the local chain stiffness, those interactions lead to a very sharp, cooperative association. This scenario is of relevance to the association of DNA with surfactants and compact proteins such as RecA. External tension exerted on the chain is found to significantly modify the binding by suppressing the fluctuation-induced interaction.

[The medical faculty in Vienna during the nineteenth century]. / Den medicinska fakulteten i Wien under 1800-talet.

To understand the enormous cultural dominans of Vienna during the 19-teenth century it is necessary to know some of the long history of the Habsburg empire. It was created as early as 1276. The Vienna medical faculty got its first strong position during the middle of the 18-teenth century. Vienna became the political and cultural centre as capital of the empire. From all parts of the many cultural country the intelligentsia came to the city. The development in all fields of culture: music, literature, art, and architecture was impressing. After the revolution in 1848 the medical faculty changed its policy and the so called second Vienna School was established. The pathologist Carl von Rokitansky played a decisive role both as administrator and as scientist. Many famous doctors and scientists gave the medical faculty a world-wide reputation and pupils from all over the world found Vienna to be a medical Mecca. In many medical specialities Vienna took the leading position. At the same time the faculty became a centre for bitter priority fights. One of the reasons for that was the vast collection of representatives from different nationalities and ethnic groups. The era of greatness began to diminish when it got to its end when the Austrian-Hungarian double monarchy fell into pieces in 1916 and disappeared definitely in 1938 after the German annexation.

Franz Kafka, Sigmund Freud and Markus Hajek. A connection in life and death.

When Sigmund Freud was taken ill in 1923 with a malignant tumor of his right upper jaw he was initially treated by the famous Viennese rhino-laryngologist, Professor Markus Hajek. One year later, Franz Kafka, who was suffering from pulmonary tuberculosis which had spread to the larynx, was likewise placed under the care of this distinguished specialist. Neither of the encounters proved beneficial from the professional point of view and both well-known patients received remarkably poor attentions in keeping with the general autocratic attitude by clinical chiefs of the time in Vienna. Franz Kafka was terminally ill when he came to Hajek and no treatment was yet available for the disabling and painful laryngeal complication of his advanced tuberculosis. He died about a month after leaving Hajek's ward in Vienna. Sigmund Freud required repeated subsequent operations on his jaw and the insertion of a prothesis. Hajek had handed Freud over to Hans Pichler for further care and it was entirely due to the skill of this extremely competent and empathetic maxilliary surgeon that Freud lived for another 16 years, working to almost full capacity.

[Glimpses from the history of otitis media]. / Glimtar ur öroninflammationens historia.

The history of otitis media has much in common with the history of other infectious diseases. Over the years France, England and Germany respectively dominated the field and treatment of otitis media. During the French period (eighteenth and nineteenth century), Louis Petit for the first time performed an operation with opening of the mastoid cells. In the last decades of the nineteenth century, during the English period, many famous ear doctors spread their names over the world, namely J. Toynbee, J. Hinton and W. Wild of which the latter 1853, wrote the first text book in the field called "Practical observations on aural surgery and the nature and treatment of diseases of the ear." During the German period the surgical treatment (mastoidectomy) of otitis media and its sequele was fullfilled by A. von Tröltsch, H. Schwartze and A. Politzer who together started the first journal "Archiv für Ohrenheilkunde". Politzer also 1873, started the first ear clinic in Europe, in Vienna. It was almost a rule, that all ear surgeons in Europe during that time, had to visit the ear clinic in "Allgemaines Krankenhaus" in Vienna to gain a proper education. 1940 B. Chain, V. Fleming and H. Florey invented the penicillin and were rewarded with the Nobel prize, and from then on the treatment of otitis media changed dramatically.

[Brühl's collection of anatomical specimens at the ear clinic of the Karolinska hospital]. / Brühls samling av anatomiska preparat på Karolinska sjukhusets öronklinik.

Gunnar Holmgren, professor in oto-rhino-laryngology at the Sabbatsbergs Hospital in Stockholm, had in 1921 the opportunity to buy a unic temporal bone collection from Germany. As sponsor served the first Swedish, female specialist in oto-rhino-laryngology, Marta P:son Henning. The collection consists of three different sections, namely temporal bones with normal variations as well as under pathological conditions, pathological samples preserved in formalin and about 1000 microscopical slides. This collection is now situated at the ENT clinic, Karolinska Hospital, Stockholm in its total former condition. The article discusses the circumstances under which the collection was collected.

HLA antigens in patients with otosclerosis.

Seventy-four (50 females and 24 males) consecutively sampled patients with otosclerosis were tissue typed for HLA A and B antigens. There was no significant increase in any A or B antigen, but the frequency of B40 was significantly lower (p less than 0.05) in patients than in blood donors. No significant difference in HLA antigen frequencies was found between men and women, or in patients with vs. without a family history of otosclerosis.