Nonviscous Solutions Research Articles

Surface gravity waves in the presence of vertically shearing current and eddy viscosity

Conventional models of surface gravity waves usually use potential theory in their calculations where the governing equations are the inviscid Euler equations. Nevertheless, turbulence may play a significant role for short waves or highly energetic sea or river conditions and, therefore, must be taken into account in the flow's formulation. This work extends the model of linear monochromatic waves in the presence of vertically shearing currents to account for turbulence in the form of eddy viscosity varying in depth. The boundary value problem is found to be governed by an augmented Orr–Sommerfeld(–Squire) equation(s) in two-(three-)dimensional with additional terms of viscosity derivatives. The free-surface conditions are extended to account for shearing currents with turbulent viscosity and external stress for the air layer. This provides a fundamental model for investigating the influence of the turbulent viscosity on the oscillatory wave flow. Examples of semi-analytical and numerical solutions show a fundamentally different dynamical behavior with respect to the known non-viscous solutions. These differences include two regimes in the dispersion relation with non-dispersive short waves and dispersive longer waves with a reduced celerity. They also include tilted stream function contours (i.e., a phase which is a function of depth), much deeper penetration depth, and more. These preliminary results show that turbulence potentially has great importance in wave generation mechanisms as well as in highly turbulent regions such as under strong storms or cyclones.

Interfacial Reinitiation of Free Radicals Enables the Regeneration of Broken Polymeric Hydrogel Actuators

Interfacial Reinitiation of Free Radicals Enables the Regeneration of Broken Polymeric Hydrogel Actuators

Dentin tubule occlusion by a 38% silver diamine fluoride gel: an in vitro investigation

Objective Silver diamine fluoride (SDF) is effective in treatment of dentin hypersensitivity and caries lesions. However, the non-viscous solution does not easily allow clinicians to control the application area. A 38% SDF experiment gel was compared in vitro to commercial SDF for its ability to penetrate and occlude dentinal tubules.Materials and methodsHuman root surface dentin specimens were treated with gelled or standard 38% SDF or negative control. Penetration behavior was established by Drop Shape Analysis. Precipitates at the surface and within tubules were analyzed by SEM and EDX after treatment; Results: penetration depths up to 500 µm were observed for both SDF formulations. Both formulations occluded dentinal tubules similarly. Precipitates on the dentin surface and within dentinal tubules were found for both SDF formulations, with a slight tendency for the experimental gel SDF product to be more abundant than the commercially available one. Discussion: behavior of the experimental 38% SDF gel formulation appeared indistinguishable from the commercial 38% SDF product with respect to dentinal tubule penetration and occlusion.ConclusionsThe experimental 38% SDF gel may be a suitable intervention for the prevention of dentin hypersensitivity.

Investigation of the distribution of particles of drugs with the help of cascade impactor

BACKGROUND. Successful nebulization is a result of joint usage of nebulizer and medication, which equally define availability and disposition of the active substance. Amount of the substance delivered by different nebulizer systems may differ in more than 10 times.
 OBJECTIVE. The aim of the study was to investigate the distribution of aerosol particles of drugs for inhalation manufactured by «Yuria-Pharm» under conditions of usage of Ulaizer Home.
 MATERIALS AND METHODS. We investigated Ulaizer Home nebulizer and medications for inhalation (Decasan, Lorde hyal, Nebufluson, Nebutamol) with the help of new generation impactor (“Copley Scientific Limited”, Great Britain).
 RESULTS AND DISCUSSION. Mass median aerodynamic diameter (MMAD) of Decasan particles was 4.878 µm, geometric standard deviation (GSD) – 1.72. MMAD of Lorde hyal particles was 3.194 µm, GSD – 1.556. Drop distribution for Nebutamol was alike the distribution for non-viscous aqueous solutions (MMAD – 5.363 µm, GSD – 1.924). For Nebufluson MMAD was 5.491 µm, GSD – 1.724.
 CONCLUSIONS. The delivery of the inhaled drug to the required area of the respiratory system is a key to successful nebulization. It directly depends on the parameters of the aerosol. The distribution of particles of drugs manufactured by «Yuria-Pharm» in case of nebulization using Ulaizer Home allows to deliver the required amount of drug to the predefined parts of the respiratory system.

Viscosity-Mediated Growth and Coalescence of Surface Nanodroplets

Solvent exchange is a simple method to produce surface nanodroplets on a substrate for a wide range of applications by displacing a solution of good solvent, poor solvent, and oil (solution A) by a poor solvent (solution B). In this work, we show that the growth and coalescence of nanodroplets on a homogeneous surface is mediated by the viscosity of the solvent. We show that at high flow rates of viscous solution B, the final droplet volume deviates from the scaling law that correlates the final droplet volume to the flow rate of nonviscous solution B, reported in previous work. We attribute this deviation to a two-regime growth in viscous solution B, where transition from an initial, fast regime to a final slow regime is influenced by the flow rate. Moreover, viscous solution B hinders the coalescence of growing droplets, leading to a distinct bimodal distribution of droplet size with stable nanodroplets in contrast to a continuous size distribution of droplets in nonviscous case. We demonstrate that the group of small droplets produced in a high-viscosity environment may be applied for enhanced fluorescence detection with higher sensitivity and shorter response time. The finding of this work can potentially be applied for mediating the size distribution of surface nanodroplets on a homogeneous surface without templates.

Qualification and Performance Evaluation of an Automated System for Compounding Injectable Cytotoxic Drugs

Abstract Background Use of automated systems for the production of chemotherapy will increase in answer to hospitals’ needs to rationalise production. The aim of the study was to evaluate the performance of a PharmaHelp® automated system for compounding chemotherapy. Methods Viable and non viable particles in air and liquid were measured by particle counter. Surface chemical contamination was simulated with a quinine solution. Microbiological contamination and aseptic processes were studied using media-fill tests. Dose accuracy was evaluated using a gravimetric method, in simulation studies and with real products in daily practice. Productivity was calculated by batch of ten IV-bags. Results No particles or microbiological contamination were detected. Filling was accurate for all the volumes of non-viscous solution studied (97–103 %). Minimum volumes which could be prepared accurately were 2 mL and 5 mL for the non-viscous and viscous solutions, respectively. For 2–5 mL volumes, the robot was less accurate than average, and 0–2 % of bags were rejected (deviation>10 %). Average fill deviations were from 0–3 % for 2–5 mL volumes and<1 % for volumes above 5 mL. Average production time for ten bags was 61±11 min. Conclusions The automated system was able to produce chemotherapy effectively, delivering appropriate quality with productivity comparable to manual preparations. These results confirmed that such automated systems have the potential to guarantee optimal safety for patients and technicians.

A Fast and Convenient Way to Predict Relaxation During a Frequency-Selective Adiabatic Hyperbolic Secant Pulse (HS1 Sech Pulse)

Frequency-selective inversion of magnetization is often achieved by long, low-power adiabatic RF pulses. Because these pulses can last hundreds of milliseconds, substantial relaxation of magnetization can occur during their application. Recently, a numerical model was introduced that allows an approximation of relaxation during frequency-selective adiabatic pulses for fast-tumbling small molecules in non-viscous solutions using only standard T1 and T2 relaxation times. This model is now extended to conditions in which net magnetization is not at its thermodynamic equilibrium prior to the adiabatic inversion. Simulated and experimental data reveal that the amplitude of net magnetization after an adiabatic inversion with the HS1 hyperbolic secant pulse can be approximated by a linear function of the magnetization before the pulse, depending only on T1 and T2 relaxation. The model presented here is particularly applicable to solvent-suppression sequences that utilize multiple adiabatic inversions, such as the multiple inversion-recovery nulling sequence EXCEPT. Tabulated slope and intercept values for the linear relationship are provided to facilitate a convenient optimization of pulse sequences that utilize HS1 frequency-selective adiabatic inversions.

Mechanically Induced Gelation of a Kinetically Trapped Supramolecular Polymer

The stimuli-induced gelation of a urethane-functionalized ditopic ureidopyrimidinone (UPy) compound is presented, and the mechanism by which the gelation proceeds is proposed. In a 40–120 mM solution in chloroform, the compound can exist in two different aggregated states, namely a low viscous mixture of (cyclic) oligomers or a fibrous gel. As evidenced by IR, NMR, and WAXS, the liquid state is stabilized by hydrogen bonds between the UPy and the back-folded chain, while the fibrous gel is stabilized by lateral hydrogen bonds within stacked UPy dimers. Controlled preparation techniques allow for pathway selection to arrive at one of both states. The remarkable long-term stability of the low viscous state (over 2 months for a 80 mM solution) is in contrast to the fast transformation into a gel by stirring in a few hours. Other mechanical stimuli like shaking, sonicating, and stirring for a shorter period, as well as freezing and thawing the solution, yield weaker gels than those obtained by long stirring. Heating the gels and slow cooling reversibly yield the nonviscous solution. This shows that the formation of UPy–urethane hydrogen bonds kinetically traps the UPy polymers, thereby preventing their lateral aggregation. The application of mechanical stress or freezing disrupts this interaction, allowing for the formation of a stacked nucleus on which further material can grow, eventually leading to gelation of the solution.

Thermographic assessment of the thenar thumb muscles during pipetting

Hand disorders as a result of pipetting are common because of its nature (repetitive, precise, controlled movements, sustained forces, etc.). Techniques to quantify risk factor exposures are needed to understand pathophysiological mechanisms associated with musculoskeletal disorders. Therefore, an exploratory study was conducted to assess the value of thermography as a potential assessment tool during pipetting. Temperatures of the skin surface over the thenar thumb muscles were collected from 12 participants (six males and six females) while using high or low volume pipettes to transfer viscous or non-viscous solutions between tubes. Subjective ratings of discomfort were also collected. Rate of change in thermal readings and perceived discomfort over time was observed, and a moderate correlation (r = 0.47) between these variables was found. Gender was found to significantly affect the thermal readings. These results suggest that thermography may be potentially used to further understand pathophysiological mechanisms for upper extremity musculoskeletal disorders.

A new method for constructing exact solutions to three-dimensional Navier-Stokes and Euler equations

Formulas are derived that make it possible to construct new exact solutions for three-dimensional stationary and nonstationary Navier-Stokes and Euler equations using simpler solutions to the respective two-dimensional equations. The formulas contain from two to five additional free parameters, which are not present in the initial solutions to the two-dimensional equations. It is important that these formulas do not contain quadratures in the steady-state case. We consider some examples of constructing new three-dimensional exact solutions to the Navier-Stokes equations using the derived formulas. The results are used to solve some problems of the hydrodynamics of a viscous incompressible liquid. Examples of thenonuniqueness of solutions to steady-state problems are given. Some three-dimensional solutions to the Navier-Stokes equations are constructed using nonviscous solutions to the Euler equations. Two classes of new exact solutions to the Grad-Shafranov equation that contain functional arbitrariness are specified. Note that, in this study, a new method for constructing exact solutions is applied that can be useful for analyzing other nonlinear physical models and phenomena. Several physical and physicochemical systems where this method can be used are considered.

The Potassium Channel KAT1 Is Activated by Plant and Animal 14-3-3 Proteins

14-3-3 proteins modulate the plant inward rectifier K+ channel KAT1 heterologously expressed in Xenopus oocytes. Injection of recombinant plant 14-3-3 proteins into oocytes shifted the activation curve of KAT1 by +11 mV and increased the tau(on). KAT1 was also modulated by 14-3-3 proteins of Xenopus oocytes. Titration of the endogenous 14-3-3 proteins by injection of the peptide Raf 621p resulted in a strong decrease in KAT1 current (approximately 70% at -150 mV). The mutation K56E performed on plant protein 14-3-3 in a highly conserved recognition site prevented channel activation. Because the maximal conductance of KAT1 was unaffected by 14-3-3, we can exclude that they act by increasing the number of channels, thus ruling out any effect of these proteins on channel trafficking and/or insertion into the oocyte membrane. 14-3-3 proteins also increased KAT1 current in inside-out patches, suggesting a direct interaction with the channel. Direct interaction was confirmed by overlay experiments with radioactive 14-3-3 on oocyte membranes expressing KAT1.

The Solvent Protection of Alzheimer Amyloid-β-(1–42) Fibrils as Determined by Solution NMR Spectroscopy

Alzheimer disease is a neurodegenerative disorder that is tightly linked to the self-assembly and amyloid formation of the 39-43-residue-long amyloid-beta (Abeta) peptide. Considerable evidence suggests a correlation between Alzheimer disease development and the longer variants of the peptide, Abeta-(1-42/43). Currently, a molecular understanding for this behavior is lacking. In the present study, we have investigated the hydrogen/deuterium exchange of Abeta-(1-42) fibrils under physiological conditions, using solution NMR spectroscopy. The obtained residue-specific and quantitative map of the solvent protection within the Abeta-(1-42) fibril shows that there are two protected core regions, Glu11-Gly25 and Lys28-Ala42, and that the residues in between, Ser26 and Asn27, as well as those in the N terminus, Asp1-Tyr10, are solvent-accessible. This result reveals considerable discrepancies when compared with a previous investigation on Abeta-(1-40) fibrils and suggests that the additional residues in Abeta-(1-42), Ile41 and Ala42, significantly increase the solvent protection and stability of the C-terminal region Lys28-Ala42. Consequently, our findings provide a molecular explanation for the increased amyloidogenicity and toxicity of Abeta-(1-42) compared with shorter Abeta variants found in vivo.

Viscosity Dependence of the Magnetic Field Effect Due to the ΔgMechanism

We investigated the magnetic field effect on the yields of the escaping radicals formed by the hydrogen abstraction reaction of excited triplet 4-methoxybenzophenone with 4-chlorothiophenol in mixtures of 2-propanol and cyclohexanol. The yields of the escaping radicals decreased with increasing external magnetic field owing to the Δg mechanism. The relative yield of the escaping radicals to that in the absence of the external magnetic field in 2-propanol was 0.9 at 1.4 T. The magnetic field effects in a nonviscous solution such as 2-propanol were proportional to the square root of the external magnetic field and the solvent viscosity, (Bη)1/2. However, the deviation from this relationship, the decrease in the exponent, was observed by increasing the solvent viscosity, up to 60 cP. The relative yield in cyclohexanol was 0.88 at 0.8 T and roughly constant up to 1.4 T.

Atomic “After Effects” Following181Hfβ--Decay

Strong evidence of atomic “after effects” following β−-decay of 181Hf was observed from perturbed angular correlation (PAC) studies in different viscous and non-viscous molecular solutions and in ionic as well as non-ionic solutions. In non-viscous acetone and H2O solutions, the PAC spectra have been found to be completely different to what was expected considering molecular motions in these media. Similarly, in the glycerol-H2O system, PAC spectra remain significantly unchanged with the change of viscosity indicating that molecular motions are not reflected in these media. Rather, perturbations from the interaction of the nucleus-excited atomic state, which was so far considered to be absent for 181Hf β−-decay, have been found to be dominant. The atomic shell recovery times in molecular liquids have been found to be in the range 50–150 nsec. In insulating solid HfCl4 medium, however, the PAC spectrum indicates that the atomic shell following 181Hf β−-decay remains unchanged within the lifetime of the intermediate state. The lifetime for the 615 keV level has been remeasured and a value of T1/2=12.1±0.1 nsec only has been obtained. This value, although in strong disagreement with the earlier reported value (17.83 μsec), helps explain atomic “after effects” in 181Hf β−-decay.

Fluorescence quenching kinetics in short polymer chains: Dependence on chain length

Monte Carlo simulations of chain conformations and the diffusion equation were used to analyze the fluorescence kinetics of short polymer chains labeled with a probe and a quencher at opposite ends. In simulations, three chain models were considered: an ideal chain (without volume interactions); a self-avoiding chain taking into account the exclusive volume effect; and a self-avoiding chain with limited flexibility between nearest segments. For each model, end-to-end distance distribution functions were obtained, which were different from Gaussian ones. The distribution functions were used in a diffusion equation to simulate the fluorescence kinetics of the probe affected by intramolecular end-to-end collisions of short chains. The kinetics has been numerically calculated for a representative experimental system in a nonviscous solution. The simulated time-resolved fluorescence decays were monoexponential except at very short times (<2 ns). Diffusion coefficients were calculated for different chain models and different chain lengths. The experimental data could be reproduced by assuming systematically smaller end-to-end diffusion coefficients for the shorter chains.

P-269. Inhibition of postoperative adhesions by a non-viscous polymer solution, Adept

P-269. Inhibition of postoperative adhesions by a non-viscous polymer solution, Adept

Polymerization of Rodlike Micelles

A new polymerizable surfactant, cetyltrimethylammonium 4-vinylbenzoate (CTVB), has been prepared and investigated. In aqueous solution, highly entangled rodlike aggregates are formed at millimolar surfactant concentrations. Free-radical polymerization of the surfactant counterions results in nearly complete conversion to a stable, nonviscous solution. Small-angle neutron scattering reveals that the micellar diameter of 40 A is unchanged during the polymerization process and that the final polymerized micelle length (400−1200 A) is determined by the relative initiator concentration. In addition, the parent rodlike micellar aggregates rearrange into spherical micelles at elevated temperature, whereas the polymerized structures are insensitive to temperature changes or dilution.

Viscosity-dependent fluid dynamics of eyedrops on the ocular surface

To determine whether the viscosity of eyedrops affects the distribution of the precorneal tear film. Using a differential pachymetry map, we obtained tear film thickness in healthy volunteers before and after the instillation of nonviscous, aqueous artificial tears and a 0.3% sodium hyaluronate solution. The instillation of aqueous artificial tears disclosed a significant (P < .05) thickening of the superior corneal tear film compared with the inferior corneal tear film. The increase in thickness by 0.3% sodium hyaluronate solution was uniform, with no differences between the superior and inferior cornea. Aqueous artificial tears caused an uneven thickening of the precorneal tear film, with most of the thickening observed at the superior cornea. Lower sections of the cornea may benefit less from the instillation of nonviscous solutions.

Separation of DNA sequencing fragments up to 1000 bases by using poly(ethylene oxide)-filled capillary electrophoresis

We have demonstrated that DNA bases up to 1000 base pairs (bp) in a sequencing ladder can be separated using poly(ethylene oxide)-filled capillary electrophoresis (resolution of raw data=0.5 at 966 bp). Separation performance of this sieving matrix has been tested under different experimental conditions. It was found that the electric field strength played a critical role in the onset of reptation and thus the separation efficiency. Optimized gel composition and concentration is required for good separation, but the total gel concentration should lie between 2.5 and 3.0%. We observed that the capillary length influences the number of theoretical plates and the maximum readable length of DNA. For sequencing up to 500 bp, relatively nonviscous solutions can be used, greatly facilitating the replacement of the sieving matrix in between runs.

Effect of viscosity on the stability of an interface subjected to high-frequency magnetic fields

Natural frequencies and stability criterion for an interface between a liquid metal and an insulating gas subjected to a parallel alternating magnetic field are obtained, with particular attention to the influence of the small viscosity of the liquid metal. The governing equations are derived under the assumption of small magnetic Reynolds number and the neglect of thermal effects. Results indicate that when the liquid metal is above the insulating gas the viscous-magnetic terms may play the role of a negative viscosity, leading to overstability close to the nonviscous critical solution of Rayleigh–Taylor type. Thus, the criterion of stability changes. Apart from this region of overstability the natural frequencies of the nonviscous and viscous solutions are very similar, the changes being of the order of the nondimensional viscosity. Similarly, the velocity perpendicular to the interface does not deviate appreciably from the nonviscous solution. On the contrary, the tangential velocity differs markedly from the nonviscous solution.