Comparison of two cold atmospheric pressure plasma jet configurations in argon

The present study compares the operation of two cold atmospheric plasma jet (CAPJ) configurations: needle-to-cylinder electrode configuration (CAPJ I) and single high-voltage cylinder electrode around the quartz tube (CAPJ II). The CAPJs were operated in argon flowing through a quartz capillary with 0.5-mm inner diameter into the ambient air, and the plasma was generated by sinusoidal kHz frequency AC power supplies. The main emphasis of the study was on the mechanism of the initiation of ionization waves for these two configurations. For both CAPJs, there appeared several ionization waves during one half-period of the applied voltage waveform, and the number of ionization waves increased at higher voltage amplitudes. However, we discovered marked differences in the initiation of the ionization waves for two different CAPJ configuration. The applied voltage controlled the initiation of consecutive ionization waves, which propagated from the grounded electrode towards the tube orifice in CAPJ I. In the case of CAPJ II, certain time had to pass for the initiation of a new ionization wave, and subsequent ionization waves within the same half-period started at the tube orifice. In addition to the differences in the initiation of the ionization waves, we observed that the CAPJ I was ignited and sustained at lower voltages, while CAPJ II produced a longer plasma jet. The observed advantages and deficiencies of investigated CAPJ configurations point out their potential in different applications.     

Versatile Use of Chitosan and Hyaluronan in Medicine

Chitosan is industrially acquired by the alkaline N-deacetylation of chitin. Chitin belongs to the β-N-acetyl-glucosamine polymers, providing structure, contrary to α-polymers, which provide food and energy. Another β-polymer providing structure is hyaluronan. A lot of studies have been performed on chitosan to explore its industrial use. Since chitosan is biodegradable, non-toxic, bacteriostatic, and fungistatic, it has numerous applications in medicine. Hyaluronan, one of the major structural components of the extracellular matrix in vertebrate tissues, is broadly exploited in medicine as well. This review summarizes the main areas where these two biopolymers have an impact. The reviewed areas mostly cover most medical applications, along with non-medical applications, such as cosmetics.     

Antioxidative properties of <Emphasis Type="Italic">Sambucus nigra</Emphasis> extracts

Potential protective effects of elderberry (Sambucus nigra) extracts against oxidative degradation of hyaluronan (HA) were detected in vitro. To induce free-radical-mediated HA degradation, Weissberger’s biogenic oxidative system, which mimics the situation of acute inflammation, was applied. Time- and dose-dependent changes of dynamic viscosity of the HA solutions in the presence and absence of two elderberry extracts produced in 2006 and 2012 were recorded by rotational viscometry (RV). Radical scavenging capacity of both extracts was investigated by the spectrocolorimetric ABTS [2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt] assay and the “inverted” ABTS assay. Oxygen consumption of the system oxidizing HA either in the absence or presence of the elderberry extracts was determined. The results of RV revealed that an addition of the newer extract (2012) promoted the inhibition of HA degradation more markedly compared to the older extract (2006). The same effect of both extracts on ABTS^·+ scavenging was observed. Inverted ABTS assay demonstrated that colorful substances were not responsible for the radical-scavenging activity. Results of oximetry demonstrated that the effect of the extract from 2006 was more significant than that of the extract from 2012.     

Stimulated Raman scattering in natural crystals of fluorapatite,Ca5(PO4)3F

Hexagonal Ca₅(PO₄)₃F, known as natural crystal fluorapatite and oldest host‐crystal for Ln³⁺‐lasant ions, is presented as a Raman‐active material. High‐order Raman‐induced χ⁽³⁾‐nonlinear processes are discovered in natural crystals of fluorapatite under picosecond pumping at 1.064 μm and 0.532 μm wavelength. A multitude of Stokes and anti‐Stokes components is generated in the ultraviolet, visible and near‐infrared spectral region by stimulated Raman scattering (SRS) and Raman four‐wave mixing (FWHM), resulting in a frequency comb with a width of 520 THz. The spectral lines are identified and attributed to the ν₁(A_g) vibration mode of the tetrahedral [PO₄] units which is related to a Raman shift of ω_SRS ≈ 965 cm⁻¹. The first Stokes steady‐state Raman gain coefficient in the near‐infrared spectral range is estimated to be >0.38 cm·GW⁻¹. Finally, a short review of SRS‐promoting vibration modes and observed χ⁽³⁾‐ nonlinear interactions in all known SRS‐active natural crystals (minerals) is given.

     

Evolutive and nonlinear vibrations of rotor on aerodynamic bearings

The use of air as a lubricant in aerodynamic bearings is advantageous, particularly in the food industry. Aerodynamic bearings with tilting pads have complicated stiffness and damping properties and need a very detailed theoretical and experimental research. Response curves of rigid rotor supported on aerodynamic bearings are presented for a linear but evolutive mathematical model. Due to non-monotone properties of stiffness and damping matrices at variable revolutions, a new resonance appears. The mathematical model of rotor vibrations in the whole area of bearing clearance is also developed in the consideration of strongly nonlinear properties of aerodynamic bearing.     

Formation of porous polymer morphology by microsyneresis during divinylbenzene polymerization

This article describes the investigation of the importance of various reaction conditions on microsyneretic pore formation during polymerization of divinylbenzene (DVB) under so‐called “solvothermal” conditions. To induce microsyneretic pore formation, the most important parameter is an unusually high dilution of monomers with a “good” porogen solvating the polymer chains. High dilution and solvation of the growing poly(DVB) chains promote the prolongation of the polymer chains rather than their interconnection by crosslinking. Consequently, when the polymer gel density reaches the point where syneresis starts, the polymer network is geometrically too extensive to be broken up into precipitating entities and, instead, porogen droplets are formed within the continuous polymer gel. The pore geometry created by microsyneresis offers high surface area in wide mesopores and hence, high capacity for supporting functional groups or reactions with much better accessibility than narrow pores between polymer microspheres produced by macrosyneresis in conventional styrenic polymer supports. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 774–781     

CZE study on adsorption processes of aliphatic and aromatic amines on PMMA chip

Adsorption processes on a PMMA chip linked with CZE separations of a group of 13 aliphatic and aromatic mono‐ and di‐amines were studied. Due to the lack of chromophores within aliphatic amines, contact conductivity detection implemented directly onto the chip was used for monitoring of cationic CZE separations. To prevent an adsorption of studied amines to the chip channels, the surface of PMMA chip was modified by dynamic coating. Different surface modifiers, such as aliphatic oligoamines (diethylenetriamine and triethylenetetramine), were added to the BGE solutions filling the chip channels. The effect of various concentrations of surface modifiers on peak profiles and separation parameters of amines was monitored. Of these, mainly, aliphatic di‐amines and aromatic mono‐amines adversely affected the CZE resolution of a whole group of analytes by their strong adsorption to the chip channels. A propionate BGE with pH 3.2 containing 100 μM triethylenetetramine and 25 mM 18‐crown‐6‐ether was found suitable for CZE resolution of 12 from a total of 13 amines studied. Simple dynamic modification of the surface of PMMA chip enabled fast (analysis time lasted 9 min), sensitive (sub‐μM LODs reached) and reproducible (1–3% RSD of the peak areas) CZE analysis of the aliphatic and aromatic amines.