Hyaluronan orders water molecules in its nanoscale extended hydration shells.

Hyaluronan (HA) is an anionic, highly hydrated bio-polyelectrolyte found in the extracellular environment, like the synovial fluid between joints. We explore the extended hydration shell structure of HA in water using femtosecond elastic second-harmonic scattering (fs-ESHS). HA enhances orientational water-water correlations. Angle-resolved fs-ESHS measurements and nonlinear optical modeling show that HA behaves like a flexible chain surrounded by extended shells of orientationally correlated water. We describe several ways to determine the concentration-dependent size and shape of a polyelectrolyte in water, using the amount of water oriented by the polyelectrolyte charges as a contrast agent. The spatial extent of the hydration shell is determined via temperature-dependent measurements and can reach up to 475 nm, corresponding to a length of 1600 water molecules. A strong isotope effect, stemming from nuclear quantum effects, is observed when light water (H2O) is replaced by heavy water (D2O), amounting to a factor of 4.3 in the scattered SH intensity.

Polyelectrolytes induce water-water correlations that result in dramatic viscosity changes and nuclear quantum effects.

Ions interact with water via short-ranged ion-dipole interactions. Recently, an additional unexpected long-ranged interaction was found: The total electric field of ions influences water-water correlations over tens of hydration shells, leading to the Jones Ray effect, a 0.3% surface tension depression. Here, we report such long-range interactions contributing substantially to both molecular and macroscopic properties. Femtosecond elastic second harmonic scattering (fs-ESHS) shows that long-range electrostatic interactions are remarkably strong in aqueous polyelectrolyte solutions, leading to an increase in water-water correlations. This increase plays a role in the reduced viscosity, which changes more than two orders of magnitude with polyelectrolyte concentration. Using D2O instead of H2O shifts both the fs-ESHS and the viscosity curve by a factor of ~10 and reduces the maximum viscosity value by 20 to 300%, depending on the polyelectrolyte. These phenomena cannot be explained using a mean-field approximation of the solvent and point to nuclear quantum effects.

Comment on "Water-water correlations in electrolyte solutions probed by hyper-Rayleigh scattering" [J. Chem. Phys. 147, 214505 (2017)].

The work by Shelton [J. Chem. Phys. 147, 214505 (2017)] discussed and interpreted differences with a previous study by Chen et al. [Sci. Adv. 2, e1501891 (2016)] regarding the influence of electrolytes on the structure of water. It is argued by Shelton [J. Chem. Phys. 147, 214505 (2017)] that impurities and hyper-Raman scattering contributions are the reasons for differences in the measured second harmonic intensity between the above two studies. Here, we show that these proposed effects are not relevant and discuss the influence of pulse parameters, focusing on pulse duration, since these two sets of experiments are performed with substantially different pulse durations, 100 ns and 190 fs, respectively. We show that inelastic higher-order effects play a role in the experiment with 100 ns laser pulses (the probed structure is that of the electrolyte solution that is modified by a laser pulse), while in the experiment with 190 fs laser pulses, only the elastic second-order response is measured (probing the unperturbed water structure).

Suicide prevention program in the Army of Serbia and Montenegro.

Suicide, as one of the greatest problems of maladjustment to the military environment, has been a subject of investigation in the Army of Serbia and Montenegro (former Yugoslav Army) for more than six decades. The Suicide Prevention Program was implemented in December 2003. The aim of the study was to follow-up the application of the Suicide Prevention Program in the Army of Serbia and Montenegro and its effect on the suicide rate and to compare its incidence in civilians. Results of the program application showed that the number of suicides in the Army of Serbia and Montenegro was constantly reducing over the period 2004 to 2005. For soldiers, it was even four times less than in the civilian male population, particularly in the period of adaptation to the military environment. Since the Suicide Prevention Program in the Army of Serbia and Montenegro proved to be successful in decreasing the suicide number, it should be further improved and routinely applied.

[The Miller-Fisher syndrome (clinical report)]. / Sindrom Miller-Fisher (klinicki prikaz).

The authors present a case report of two female patients, aged 16 and 33. Both patients had the same sudden onset of illness, with diplopia and nystagmus and very severe ataxia. The younger patient had absent tendon reflex, while the older one had the tendon reflex preserved. The younger patient had the triparesis present, both patients had no sphincter disorders. They did not have sensibility disturbances, except that the younger patient had hypesthesia of the soft palate (the motor function was preserved). The first patient was somnolent at the beginning. The clinical course being favourable, the younger patient recovered faster than the older one. Electoencephalogram was normal in both patients. CT of the brain was changed at one moment, locking like inflammatory changes. CSF of the younger patient, done twice, was normal. Serologic findings on viruses were normal. Electromyography in both patients showed, beside good motor velocity, the marked sensory velocity which recovered at the control check-ups. The authors present these two cases and they consider the differential-diagnostic difficulties of Fisher's syndrome compared to "brain stem encephalitis".