Formation of Highly Ordered Spherical Aggregates from Drying Microdroplets of Colloidal Suspension.

The formation of highly ordered spherical aggregates of silica nanoparticles by the evaporation of single droplets of an aqueous colloidal suspension levitated (confined) in the electrodynamic quadrupole trap is reported. The transient and final structures formed during droplet evaporation have been deposited on a silicon substrate and then studied with SEM. Various successive stages of the evaporation-driven aggregation of nanoparticles have been identified: formation of the surface layer of nanoparticles, formation of the highly ordered spherical structure, collapse of the spherical surface layer leading to the formation of densely packed spherical aggregates, and rearrangement of the aggregate into the final structure of a stable 3D quasi-crystal. The evaporation-driven aggregation of submicrometer particles in spherical symmetry leads to sizes and morphologies of the transient and final structures significantly different than in the case of aggregation on a substrate. The numerical model presented in the article allows us to predict and visualize the observed aggregation stages and their dynamics and the final aggregates observed with SEM.

High-precision temperature determination of evaporating light-absorbing and non-light-absorbing droplets.

Models describing evaporation or condensation of a droplet have existed for over a century, and the temporal evolutions of droplet radius and temperature could be predicted. However, the accuracy of results was questionable, since the models contain free parameters and the means of accurate calibration were not available. In previous work (Holyst et al. Soft Matter 2013, 9, 7766), a model with an efficacious parametrization in terms of the mean free path was proposed and calibrated with molecular dynamics numerical experiment. It was shown that it is essentially possible to determine reliably the temperature of a steadily evaporating/condensing homogeneous droplet relative to ambient temperature when the evolution of the droplet radius is known. The accuracy of such measurement can reach fractions of mK. In the case of an evaporating droplet of pure liquid, the (droplet) temperature is constant during the stationary stage of evaporation. In this paper, we show that, in many cases, it is also possible to determine the temporal evolution of droplet temperature from the evolution of the droplet radius if the droplet (initial) composition is known. We found the droplet radius evolution with high accuracy and obtained the evolution of droplet temperature (and composition) for droplets of (i) a two-component mixture of pure liquids; (ii) solutions of solid in liquid, one that is non-surface-active and another that is; and (iii) suspensions of non-light-absorbing and light-absorbing particles.

Evaporation of freely suspended single droplets: experimental, theoretical and computational simulations.

Evaporation is ubiquitous in nature. This process influences the climate, the formation of clouds, transpiration in plants, the survival of arctic organisms, the efficiency of car engines, the structure of dried materials and many other phenomena. Recent experiments discovered two novel mechanisms accompanying evaporation: temperature discontinuity at the liquid-vapour interface during evaporation and equilibration of pressures in the whole system during evaporation. None of these effects has been predicted previously by existing theories despite the fact that after 130 years of investigation the theory of evaporation was believed to be mature. These two effects call for reanalysis of existing experimental data and such is the goal of this review. In this article we analyse the experimental and the computational simulation data on the droplet evaporation of several different systems: water into its own vapour, water into the air, diethylene glycol into nitrogen and argon into its own vapour. We show that the temperature discontinuity at the liquid-vapour interface discovered by Fang and Ward (1999 Phys. Rev. E 59 417-28) is a rule rather than an exception. We show in computer simulations for a single-component system (argon) that this discontinuity is due to the constraint of momentum/pressure equilibrium during evaporation. For high vapour pressure the temperature is continuous across the liquid-vapour interface, while for small vapour pressures the temperature is discontinuous. The temperature jump at the interface is inversely proportional to the vapour density close to the interface. We have also found that all analysed data are described by the following equation: da/dt = P(1)/(a + P(2)), where a is the radius of the evaporating droplet, t is time and P(1) and P(2) are two parameters. P(1) = -λΔT/(q(eff)ρ(L)), where λ is the thermal conductivity coefficient in the vapour at the interface, ΔT is the temperature difference between the liquid droplet and the vapour far from the interface, q(eff) is the enthalpy of evaporation per unit mass and ρ(L) is the liquid density. The P(2) parameter is the kinetic correction proportional to the evaporation coefficient. P(2) = 0 only in the absence of temperature discontinuity at the interface. We discuss various models and problems in the determination of the evaporation coefficient and discuss evaporation scenarios in the case of single- and multi-component systems.

Coefficients of evaporation and gas phase diffusion of low-volatility organic solvents in nitrogen from interferometric study of evaporating droplets.

Evaporation of motionless, levitating droplets of pure, low-volatility liquids was studied with interferometric methods. Experiments were conducted on charged droplets in the electrodynamic trap in nitrogen at atmospheric pressure at 298 K. Mono-, di-, tri-, and tetra(ethylene glycols) and 1,3-dimethyl-2-imidazolidinone were studied. The influence of minute impurities (<0.1%) upon the process of droplet evaporation was observed and discussed. The gas phase diffusion and evaporation coefficients were found from droplet radii evolution under the assumption of known vapor pressure. Diffusion coefficients were compared with independent measurements and calculations (in air). Good agreement was found for mono- and di(ethylene glycols), and for 1,3-dimethyl-2-imidazolidinone, which confirmed the used vapor pressure values. The value of equilibrium vapor pressure for tri(ethylene glycol) was proposed to be 0.044 +/- 0.008 Pa. The evaporation coefficient was found to increase from 0.035 to 0.16 versus the molecular mass of the compound.

Temperature dependence of the evaporation coefficient of water in air and nitrogen under atmospheric pressure: study in water droplets.

The evaporation coefficients of water in air and nitrogen were found as a function of temperature by studying the evaporation of a pure water droplet. The droplet was levitated in an electrodynamic trap placed in a climatic chamber maintaining atmospheric pressure. Droplet radius evolution and evaporation dynamics were studied with high precision by analyzing the angle-resolved light scattering Mie interference patterns. A model of quasi-stationary droplet evolution accounting for the kinetic effects near the droplet surface was applied. In particular, the effect of thermal effusion (a short-range analogue of thermal diffusion) was discussed and accounted for. The evaporation coefficient alpha in air and in nitrogen were found to be equal. The alpha was found to decrease from approximately 0.18 to approximately 0.13 for the temperature range from 273.1 to 293.1 K and follow the trend given by the Arrhenius formula. The agreement with condensation coefficient values obtained with an essentially different method by Li et al. [Li, Y.; Davidovits, P.; Shi, Q.; Jayne, J.; Kolb, C.; Worsnop, D. J. Phys. Chem. A. 2001, 105, 10627] was found to be excellent. The comparison of experimental conditions used in both methods revealed no dependence of the evaporation/condensation coefficient on the droplet charge nor the ambient gas pressure within the experimental parameters range. The average value of the thermal accommodation coefficient over the same temperature range was found to be 1 +/- 0.05.

Serum Th1 and Th2 profile cytokine level changes in patients with Graves' ophthalmopathy treated with corticosteroids.

The aim of this study was to estimate the influence of corticosteroids on Th1 and Th2 serum cytokine balance in patients with GO: IFNgamma, TNFalpha, IL-4 and IL-10. Further, we tested the hypothesis of an up-regulation of Th2 immune response during successful treatment with corticosteroids to explain their beneficial effect in Graves' ophthalmopathy. Serum cytokines were detected in three groups of subjects: 20 patients with Graves' disease without ophthalmopathy (Gd), 16 patients with clinical symptoms of ophthalmopathy (GO) (CAS over 3 points, last consultation record for GO less than a year old) and 16 healthy volunteers. Corticosteroid therapy consisted of intravenous infusions of methylprednisolone (MP) (2 series, 3 g each time) and subsequent treatment with oral prednisone (60 mg per day) in a tapering schedule. The serum samples were collected 24 hours before MP, 24 hours after MP, 14 days of treatment with prednisone and at the end of corticosteroid therapy. The levels of IFNgamma, TNFalpha, IL-4 and IL-10 in the serum were determined using ELISA. Statistical significance was estimated by the Mann-Whitney U-test. Our findings show a deviation to systemic Th2 profile cytokines in Graves' disease. In patients with GO, we found a significantly increased serum IL-10 concentration. In corticosteroid-responsive patients, the balance of serum cytokines IL-4/IFNgamma, IL-4/TNFalpha, IL-10/IFNgamma and IL-10/TNFalpha increased and remained upregulated until the end of the study. In non-responders, the balance of serum cytokines studied increased after methylprednisolone but declined markedly during continuation of the therapy with prednisone. In summary, our results show that efficient corticosteroid therapy may be related to its influence on Th2/Th1 profile cytokine balance. The upregulation of serum IL-4 and IL-10 during successful treatment with corticosteroids indicate the possibility of using these cytokines as predictors of the beneficial effect of corticosteroids in Graves' ophthalmopathy.

High-density optical data storage with one-photon and two-photon near-field fluorescence microscopy.

A spatially localized photochemical reaction induced by near-field femtosecond laser pulses is demonstrated on a nanometer scale and used for high-density optical data storage. Recorded domains down to 120 and 70 nm are obtained with one-photon and two-photon excitation, respectively. It is shown that the local-field confinement that is due to the quadratic dependence of two-photon excitation on light intensity has the potential to increase the near-field optical storage density.

Nanoscale nonlinear optical process: theoretical modeling of second-harmonic generation for both forbidden and allowed light.

Based on a combination of the multiple-multipole method and nonlinear coupled-wave equations, a rigorous three-dimensional numerical simulation of nonlinear optical interactions between an optical near field and a nonlinear medium is performed, allowing us to study the dependence of second-harmonic (SH) near-field intensity on tip-sample distance and the polarization state of the incident fundamental wave. It is demonstrated that allowed and forbidden light make different contributions to the SH near-field intensity.

Near-field probing of nanoscale nonlinear optical processes.

We report a study of two nonlinear optical processes at the nanoscale level, using a near-field probe: (i) two-photon-pumped upconversion from ZnS:Mn nanoparticles encapsulated with 2-[{(?) -2-[4 -(ethylsulfonyl) phenyl]- 1-ethenyl} (methyl)anilino]- 1-ethanethiol and (ii) second-harmonic generation (SHG) from N -(4-nitrophenyl)- (L) -prolinol crystallites. The use of highly efficient nonlinear organic chromophores together with special processing on the nanometer scale made it possible to observe and characterize what are believed to be the smallest topographically distinguishable objects reported so far, using nonlinear optical techniques. Issues pertaining to the study of two-photon-excited emission and SHG by use of a near-field probe are discussed.

[Acceptance and subjective evaluation of intensive insulin therapy and an educational program by pregnant women with insulin dependent diabetes]. / Akceptacja i subiektywna ocena intensywnej insulinoterapii oraz programu edukacyjnego przez kobiety ciezarne z cukrzyca insulinozalezna.

The study was carried out in 71 IDDM female diabetics: 51 pregnant women aged 28.6 +/- 3.6 yrs, and 20 IDDM female patients aged 26 +/- 5 yrs. All women had been treated with intensified insulin therapy and continuous self-monitoring. All the patients participated in the five day educational programme at the beginning of therapy. The patients were requested to fill in a multiple-choice test questionnaire with questions about their knowledge of the practical aspects of diabetes, effectiveness of the educational programme, difficulties and acceptance of management. The diabetic pregnant women gave subjective estimations of the development of their children. Mean ratio of correct answers to 7 questions estimating the level of knowledge of diabetes was in diabetic pregnant patients 70% which was higher than in other IDDM female patients. 27% IDDM pregnant women estimated the course as very difficult. The main causes of difficulties in management in the investigated patients were self-estimating control of diabetes, dietary programme, frequent selfmonitoring. The majority of diabetic pregnant women (82%) and all IDDM females could and did accept the whole management programme. In conclusion the general aspects of management were accepted both by diabetic pregnant and non-pregnant women. The major difficulties were realisation of dietetic management and often estimations of glycemia during selfmonitoring of diabetes. The short, five-day educational course is beneficial in the IDDM management.

[Studies of insulinemia in obese patients]. / Badania insulinemii u pacjentów z otyloscia.

In 56 patients with simple obesity blood glucose and insulin levels were assessed under fasting conditions and after oral glucose tolerance test. Besides, several lipid metabolism parameters like triglycerides, HDL--and LDL--cholesterol were estimated, too. Direct relationship was found between the impairment of glucose tolerance and the duration of obesity and the overweight. Obese persons with higher overweight and an average duration of obesity exhibited fasting hyperinsulinemia. Irrespective of the overweight magnitude and the degree of glucose tolerance impairment a more pronounced insulin reaction to glucose was observed. The same was found in the groups of persons with the history of obesity not exceeding 15 years. Moreover, in the group of obese persons with normal glucose tolerance, in those with overweight reaching 70% and with short and moderate duration of. Fasting obese hyperinsulinemic persons showed reduced concentration of HDL--obesity the levels of triglycerides were found to be elevated.

[Evaluation of hearing in patients with diabetes]. / Ocena sluchu u chorych na cukrzyce.

Hearing in 60 diabetics aged 20-70 years were studied by means of tonal, verbal and B'ekèsy audiometry, SISI tests, Fowler tests, stapedius reflex and tone decay tests. The material was grouped according to the diabetes type, chronicity of disease, age, sex and presence of retino- and polyneuropathy. The results proved that diabetes may cause the progressive form of hearing loss which depend of chronicity of disease and age of patients. Sometimes the hypo-acuity may be found in the recent form of diabetes, rarely as sudden deafness. The hearing impairment is more frequent among the retino- and polyneuropathy patients. The localisation of lesions may be in all part of hearing pathways from the labyrinth to cortical areas.