Improving LIBS analysis of non-flat heterogeneous samples by signals mapping.

Heterogeneous material analysis by the laser-induced breakdown spectroscopy (LIBS) technique is challenging in real practice due to requirements for representative sampling and non-flat surfaces of the samples. Methods complementary to LIBS (plasma imaging, plasma acoustics, sample surface color imaging) have been introduced to improve zinc (Zn) determination in soybean grist material by LIBS. The detailed statistical study revealed that atomic/ionic lines emission and other LIBS signals were distributed normally except for acoustics signals. The correlation between LIBS and complementary signals was rather poor due to the large variability of the particle properties of soybean grist material. Still, analyte line normalization on plasma background emission was rather simple and effective for Zn analysis but required a few hundred spot samplings for representative Zn quantification. Non-flat heterogeneous samples (soybean grist pellets) were analyzed by LIBS mapping but it was demonstrated that the choice of sampling area is crucial for reliably analyte determination.

Combining thermal imaging and spectral pyrometry for express temperature mapping in additive manufacturing.

A compact and low-cost two-dimensional (2D) thermal imager was developed for real-time temperature mapping of a melt pool during coaxial laser cladding (the additive manufacturing technique). The device combines a color CMOS camera and a compact spectrometer. The spectrometer was utilized for internal calibration and validation of a 2D temperature map that was acquired by the CMOS camera. The remarkable feature of the thermal imager is that camera images are calibrated directly during the measurement process utilizing spectral pyrometry. Additionally, the spectrometer decreased a potential systematic error due to a spectrum contribution from atomic/ionic lines emission. The spectral pyrometry provided temperature accuracy measurements of ±23K while two-dimensional (2D) temperature mapping by two-color pyrometry accuracy was estimated as ±38K in the range of 1700-3500 K. The system has been installed at a coaxial laser cladding head for real-time temperature mapping. The system was developed for measuring a melt pool during laser cladding production of a high wear-resistant coating (tungsten carbide particles in a nickel matrix). Tungsten carbides powder flow rate has been changed sequentially from 5 to 27 g/min by powder feeder programming, which resulted in a variation of melt pool dimensions and temperature maps during the cladding process.

In situ laser-induced breakdown spectroscopy measurements during laser welding of superalloy.

Laser-induced breakdown spectroscopy (LIBS) has been utilized for in situ diagnostics of the laser welding process. The influence of different weld spot areas (melt pool, solid weld) on LIBS signals and plasma properties has been studied in detail. Liquid metal sampling and high target surface temperature of the melt enhance LIBS plasma intensity and increase plasma temperature. The influence of laser welding process parameters on LIBS measurements has been studied in order to differentiate optimal and defective laser welding. In case of defective laser welding, the melt pool was intensively boiling, so we have observed greater LIBS signals but poor reproducibility. For the first time, the LIBS technique was demonstrated to detect defective laser welding during in situ measurements utilizing atomic and ionic line comparison by paired sample t-test hypotheses testing.

Phosphine modification of proline-glycine-proline tripeptide and study of its neuroprotective properties.

BACKGROUND: Treatment of neurodegenerative diseases, such as Parkinson's disease, Huntington's chorea, Alzheimer's disease, is one of the priority directions in modern medicine. Thus, search and production of new physiologically active substances for the treatment of neurodegenerative disorders is one of the most important tasks for organic chemistry. The approach based on the replacement of a peptide bond in a peptide molecule with a structural isostere, non-hydrolyzable methylene phosphoryl fragment makes it possible to increase the metabolic stability of peptide molecules to the destructive action of peptidases. METHODS: This work is devoted to the approbation of a new synthetic approach to the production of physiologically active substances in a series of peptide-type compounds with activity by replacing the peptide bond with isosteric methylene-phosphoryl fragment with the preservation of the original amino acid sequence. RESULTS: A phosphine analog of the known physiologically active tripeptide proline-glycine-proline was obtained, cytotoxicity and neuroprotective properties of the initial tripeptide and its phosphine analog were studied. CONCLUSION: Preliminary biological tests have shown that the obtained phosphine analog of the proline-glycine-proline tripeptide is involved in modulating the formation of sediments in the cellular system of proteinopathy, which may indicate their potential antiaggregatory properties.

Surface plasma influence on nanosecond laser ablation.

The comparison of laser ablation and plasma evolution has been carried out for a molten steel sample in the absence and in the presence of surface plasma. A continuous wave (cw) laser beam was utilized for local melting of a steel (Fe>99 wt.%) sample, but it also induced a surface plasma according to optical emission spectroscopy. The cw laser was switched off for a few milliseconds to dissipate the surface plasma, but the surface temperature did not change according to optical pyrometer measurements. Molten metal was ablated by a nanosecond Nd:YAG laser pulse during cw laser operation and when it was switched off for 5 milliseconds. Comparison of laser ablation and plasma evolution in the presence and in the absence of the near-surface plasma induced by the cw laser beam has been carried out. Time-integrated plasma imaging detected slightly greater emissivity of the plasma induced during cw laser operation. The cw laser operation resulted in a twofold enhancement of the intensity of atomic lines in the spectra as well as slower decay of plasma emission. Plume temperature and electron density were slightly greater at early stages of plume expansion in surface plasma.

Optimizing laser crater enhanced Raman spectroscopy.

Raman signal enhancement by laser crater production was systematically studied for 785 nm continuous wave laser pumping. Laser craters were produced in L-aspartic acid powder by a nanosecond pulsed solid state neodymium-doped yttrium aluminum garnet laser (532 nm, 8 ns, 1 mJ/pulse), while Raman spectra were then acquired by using a commercial spectrometer with 785 nm laser beam pumping. The Raman signal enhancement effect was studied in terms of the number of ablating pulses used, the lens-to-sample distance, and the crater-center-laser-spot offset. The influence of the experiment parameters on Raman signal enhancement was studied for different powder materials. Maximum Raman signal enhancement reached 11 fold for loose powders but decreased twice for pressed tablets. Raman signal enhancement was demonstrated for several diverse powder materials like gypsum or ammonium nitrate with better results achieved for the samples tending to give narrow and deep craters upon the laser ablation stage. Alternative ways of cavity production (steel needle tapping and hole drilling) were compared with the laser cratering technique in terms of Raman signal enhancement. Drilling was found to give the poorest enhancement of the Raman signal, while both laser ablation and steel needle tapping provided comparable results. Here, we have demonstrated for the first time, to the best of our knowledge, that a Raman signal can be enhanced 10 fold with the aid of simple cavity production by steel needle tapping in rough highly reflective materials. Though laser crater enhancement Raman spectroscopy requires an additional pulsed laser, this technique is more appropriate for automatization compared to the needle tapping approach.

Optimizing laser crater enhanced Raman scattering spectroscopy.

The laser crater enhanced Raman scattering (LCERS) spectroscopy technique has been systematically studied for chosen sampling strategy and influence of powder material properties on spectra intensity enhancement. The same nanosecond pulsed solid state Nd:YAG laser (532 nm, 10 ns, 0.1-1.5 mJ/pulse) was used for laser crater production and Raman scattering experiments for l-aspartic acid powder. Increased sampling area inside crater cavity is the key factor for Raman signal improvement for the LCERS technique, thus Raman signal enhancement was studied as a function of numerous experimental parameters including lens-to-sample distance, wavelength (532 and 1064 nm) and laser pulse energy utilized for crater production. Combining laser pulses of 1064 and 532 nm wavelengths for crater ablation was shown to be an effective way for additional LCERS signal improvement. Powder material properties (particle size distribution, powder compactness) were demonstrated to affect LCERS measurements with better results achieved for smaller particles and lower compactness.

Laser-induced breakdown spectroscopy for three-dimensional elemental mapping of composite materials synthesized by additive technologies.

Three-dimensional multi-elemental mapping of composite wear-resistant coatings by laser-induced breakdown spectroscopy has been demonstrated for the first time, to the best of our knowledge. Individual clads of 1560 nickel alloy reinforced with tungsten carbide were synthesized by a co-axial laser cladding technique. Electron energy dispersive x-ray spectroscopy revealed elemental maps for major elements (W, Ni, Co, Cr, Fe) but failed to measure silicon and carbon. Laser-induced breakdown spectroscopy was utilized for elemental mapping of carbon and all other elements of interest. It was demonstrated that three-dimensional elemental profiling for a few tens of micrometers requires substantial laser spot overlapping during the scanning procedure in order to achieve good accuracy of depth measurements. Elemental maps for nickel, iron, chromium, silicon, tungsten, and carbon were quantified for 900 µm×900 µm×45 µm volume with 30 µm lateral and 4 µm depth resolution in the case of tungsten carbide particles in nickel alloy.

Double nanosecond pulses generation in ytterbium fiber laser.

Double pulse generation mode for nanosecond ytterbium fiber laser was developed. Two sequential 60-200 ns laser pulses with variable delay between them were generated by acousto-optic modulator opening with continuous diode pumping. A custom radio frequency generator was developed to produce two sequential "opening" radio pulses with a delay of 0.2-1 µs. It was demonstrated that double pulse generation did not decrease the average laser power while providing the control over the laser pulse power profile. Surprisingly, a greater peak power in the double pulse mode was observed for the second laser pulse. Laser crater studies and plasma emission measurements revealed an improved efficiency of laser ablation in the double pulse mode.

Idiopathic scoliosis, growth zones, magnetic therapy.

BACKGROUND: The study has been performed to investigate the influence of pulsed magnetic field on the bone growth plates to get new grounds of magneto therapy in AIS treatment. MATERIALS AND METHODS: Were used methods of "strong" and "weak" pulsed magnetic fields influence. RESULTS: Application of pulsed magnetic field causes an authentic inhibition of chondrocytes' active proliferation processes, decreases the index of labeled nuclei, indicating the suppression of DNA synthesis, takes place an increase in the unit weight of the more "mature" differentiated chondrocytes. The final result of these effects is the accelerated synostosis of bones' growth plates. CONCLUSION: Regardless of the reasons that cause growth infringements, the operating organ in the chain is the body's growth plate. Therefore, the appliance of magnetic fields in AIS treatment can be considered as a perspective one concerning growth plates' functional activity local management. To our point of view, the potential of magneto therapy methods in child's orthopedic treatment is significantly higher compared with modern practice.

[Effects of weak magnetic fields on the production of reactive oxygen species in peritoneal neutrophils in mice].

The influence of weak magnetic fields of different types on the rate of the formation of reactive oxygen species in mouse peritoneal neutrophils has been studied. It was found that the exposure of neutrophils activated by phorbol 12-myristate 13-acetate to the magnetic field tuned to the parametric resonance for Ca2+ ions leads to a decrease in the rate of the reactive oxygen species (ROS) generation by 23%. Conversely, the generation of ROS in neutrophils exposed to the same field but stimulated by the bacterial peptide FMLP (N-formyl-L-methionyl-L-leucyl-L-phenylalanine) increased by about 21%. Pulsed magnetic fields also changed the rate of ROS generation in phorbol-stimulated neutrophils by about 20%, but the sign of the effects observed in this case was opposite to those induced by the magnetic field tuned to the parametric resonance for Ca2+ ions.

[Effect of the extremely weak alternating magnetic fields on the regeneration of planarians and the gravitropic response of plants].

The influence of extremely weak alternating magnetic fields (EW AMF) directed colinearly to the static Earth magnetic field on the rate of regeneration of planarians and the rate of gravitropic response in the stem segments of flax has been studied. The value of bioeffects of EW AMF is determined by the parameter gamma B(AC)/f, where y is the gyromagnetic ratio of the magnetic moments induced by the orbital movements of electrons in atoms, and B(AC) and f correspond to magnetic induction and frequency of the alternating magnetic component. It was shown that the magnitude of bioeffects depends on the amplitude (at fixed 1000 Hz - frequency) and frequency (at fixed 192 nT - amplitude) of the alternating component. Maxima of bioeffects are observed at gamma B(AC)/f = 0.9; 2.75, and minor maxima gamma B(AC)/f = 4.5; 6.1. The bioeffects are absent at gamma B(AC)/f = 1.8, 3.8, 5.3, 6.7. The positions of the maxima and minima of bioeffects correspond to the theoretical prediction (at gamma = 14000 Hz/microT). Primary targets for the EW AMF of this type are the magnetic moments induced by the orbital movements of electrons in atoms.

[Effect of weak combined magnetic fields on the metamorphosis of the meal-worm beetle Tenebrio molitor].

The effects of weak combined magnetic fields adjusted to the parametric resonance for Ca2+ and K+ and extremely weak alternating magnetic field on the metamorphosis of the meal-worm beetle Tenebrio molitor have been studied. It was shown that the exposure of pupas of insects to all above-indicated types of fields stimulates the metamorphosis. However, after the exposure to weak combined magnetic fields adjusted to the parametric resonance for Ca2+ and K+, the number of insects with anomalies increases, which is not observed by the action of the weak alternating magnetic field.

[Retinoic acid as a regulator of planarian morphogenesis].

The effect of retinoic acid on regeneration of two species of asexual planarian races, Girardia tigrina and Schmidtea mediterranea, was studied. It was established that retinoic acids at physiological concentrations (10(-7)-10(-10) M) inhibit the regeneration of the head part of planarians but have no effect on tail blastema growth. It is shown that regeneration of the head part is inhibited as a result of arrest of the cell cycle of neoblasts, proliferating stem cells, during the transition from the G1/G0 to the S phase. Thus, the morphogenetic role of retinoic acids in planarians, primitive bilaterally symmetrical animals, has been demonstrated.

[Melatonin effect on the regeneration of the flatworm Girardia tigrina].

The melatonin effect on the anterior and posterior ends of a free-living flatworm Girardia tigrina was studied, as well as the variability of the mitotic activity of the stem cells (neoblasts) in the anterior and posterior postblasteme. This hormone may inhibit the regeneration of the anterior end of the animal in the physiologic-friendly concentrations of 10(-10)-10(-15) M by suppressing the mitotic activity of the neoblasts. This hormone does not affect the posterior end's regeneration; thus, its regeneration effect is significantly elective.

[Modulation of cardiac rhythms in humans exposed to extremely weak alternating magnetic fields].

The influence of extremely weak alternating magnetic fields (EW AMF) with amplitudes of < or = 2 microT on the heart rate variability in humans has been studied. The volunteers were placed in a large- volume square coils system (2x2x2 m), which provided the exposure of the whole body to extremely weak alternating magnetic fields homogeneous in amplitude. It was shown that the exposure of volunteers to different types of extremely weak alternating magnetic fields can both increase and decrease the magnitude of stress. In particular, the field tuned to the nuclear spins of hydrogen atoms (amplitude 1.6 microT, frequency 76 Hz) induces a decrease in the Baevsky's stress index, while the field tuned to the magnetic moments formed by the orbiting electrons in some atoms (amplitude 0.192 microT, frequency 3000 Hz) increases the stress index. The results obtained provide a possible explanation for the mechanism of adverse effects of some particular types of technogenic and natural extremely weak alternating magnetic fields on the human cardiovascular system.

[Chemotaxis as a method for testing of the biological effects of silver nanoparticles].

A method for assessing the abiotic efficiency of water-dispersed nano-sized silver particles is suggested. Nanoparticles were obtained by the method of biochemical synthesis in reversed micelles made from anionic surfactant bis-(2-ethylhexyl) sodium sulfosuccinate (AOT). A water dispersion of nanoparticles was prepared from the micellar solution in organic solvent by means of a special procedure. The abiotic efficiency assay is based on the capacity of cells to respond by the negative chemotaxis to chemical agents with harmful metabolic action. In plasmodium of myxomicete Physarum polycephalum, the biocide and repellent effects of silver nanoparticles, Ag+ ions, and AOT were tested in order to compare the abiotic efficiency of these substances in water solution and after introduction into agar substrate. The increase in the oscillation period, the reduction in the area of spreading, and the avoidance reaction in the spatial test, taken together, revealed a much higher repellent efficiency of silver nanoparticles as compared with that of Ag+ ions and AOT. The NSP concentrations lethal for Physarum were similar to those found earlier for bacteria and viruses. The chemotaxis-based tests applied in this study allow one to quantitatively assess cell reactions and monitor their time course. Besides, they have a much higher resolving capacity than the tests based on lethal effects of abiotic substances.

[Effects of extremely weak alternating magnetic fields on the plant gravitropism]. / Vliianie kraine slabykh peremennykh magnitnykh polei na gravitropizm rastenii.

It was shown that the rate of gravitropic response in apical segments excised from the 4-day-old seedlings of flax (Linum bienne) may be substantially influenced by combined magnetic fields (CMF) of two different types: 1) CMF tuned to the parametric resonance for Ca2+; 2) CMF containing extremely weak alternating component with the values of magnetic density ranging from 10(-6) to 10(-10) T. Our experimental data indicate that CMF affect the gravitropic response via at least two different mechanisms. The first one corresponds to the ion parametric resonance well established earlier in studies with test-systems prepared from animals. The origin of the bioeffects induced by CMF containing extremely weak alternating component remains to be established.

[Activation and inhibition of the gravitropic response in the flax stem segments exposed to the permanent magnetic field with magnetic density ranging from 0 to 350 microT]. / Aktivatsiia i ingibirovanie gravitropicheskoi reaktsii v segmentakh steblei l'na pri izmenenii velichiny magnitnoi induktsii postoiannogo polia v predelakh ot 0 do 350 mkT.

It was found that the rate of gravitropic bending in apical segments excised from 4-day-old etiolated seedlings of flax Linum bienne is strongly and nonlinearly dependent on the value of the magnetic flux density of a static magnetic field, BDC, in the range from 0 to 350 microT. The gravitropic bending is stimulated at 0 < or = BDC < or = 2 microT and 200 < or = BDC < or = 350 microT but is inhibited at 100 < or = BDC < or = 170 microT relative to control samples being in the magnetic field of the Earth equal to 46.5 microT.

[Activation and inhibition of gravitropic reaction of plants using weak combined magnetic fields]. / Aktivatsiia i ingibirovanie gravitropicheskoi reaktsii rastenii s pomoshch'iu slabykh kombinirovannykh magnitnykh polei.

It is shown that the rate of gravitropic response in the segments of stems excised from millet, flax and clover seedlings may be considerably activated or inhibited by the application of weak combined magnetic fields tuned to the parametric resonance for Ca2+ or K+, correspondingly.