Laser Treatment of Surfaces for Pool Boiling Heat Transfer Enhancement.

The laser treatment of surfaces enables the alteration of their morphology and makes them suitable for various applications. This paper discusses the use of a laser beam to develop surface features that enhance pool boiling heat transfer. Two types of structures (in the 'macro' and 'micro' scale) were created on the samples: microfins (grooves) and surface roughness. The impact of the pulse duration and scanning velocity on the height of the microfins and surface roughness at the bottom of the grooves was analyzed with a high precision optical profilometer and microscope. The results indicated that the highest microfins and surface roughness were obtained with a pulse duration of 250 ns and scanning velocity of 200 mm/s. In addition, the influence of the 'macro' and 'micro' scale modifications on the boiling heat transfer of distilled water and ethyl alcohol was studied on horizontal samples heated with an electric heater. The largest enhancement was obtained for the highest microfins and roughest surfaces, especially at small superheats. Heat flux dissipated from the samples containing microfins of 0.4 mm height was, maximally, over three times (for water) and two times (for ethanol) higher than for the samples with smaller microfins (0.2 mm high). Thus, a modification of a selected model of boiling heat transfer was developed so that it would be applicable to laser-processed surfaces. The correlation proved to be quite successful, with almost all experimental data falling within the ±100% agreement bands.

Laser Surface Alloying of Sintered Stainless Steel.

A characteristic feature of sintered stainless steel (SSS) is its porosity. Porosity results in a lower density of steel, making attractive components for producing lightweight structures and materials used in industry (e.g., the automotive industry or aerospace). Scientists also observe that porosity adversely affects steel's properties, especially its strength properties. One of the proposals for improving the discussed properties is the use of surface treatment of sintered stainless steels, e.g., with the use of concentrated energy sources such as plasma beams or laser beams. However, this proposal is an incidental subject of research, which is not justified from the point of view of the obtained research results presented by a few research groups. In this study, the surface modification (surface treatment) of sintered stainless steel was presented. The authors proposed the use of two surface treatments in order to compare them and obtain the best results. The first treatment was the deposit of Cr3C2-NiCr coatings on SSS surfaces using the atmospheric plasma spraying (APS) method. The second treatment was to create surface layers on SSSs by laser alloying the surface with a CO2 laser. Due to high precision and ease of automation, the most common methods in surface alloying treatment are laser technologies. This research's main aim was to analyze the microstructure and strength properties of the SSS surface layer. The research confirms that applying the Cr3C2-NiCr coating and modifying the surface layer through the laser alloying method improves the mechanical properties of SSSs.

The Effect of Rare Earth Metals Alloying on the Internal Quality of Industrially Produced Heavy Steel Forgings.

The paper presented the findings obtained by industrial research and experimental development on the use of rare earth metals (REMs) in the production of heavy steel ingots and their impact on the internal quality of the 42CrMo4 grade steel forging. REMs alloying was carried out after vacuuming the steel. A relatively large melting loss of cerium (about 50%) and its further decrease in casting due to reoxidation were observed. Refinement of structure and better mechanical properties of forged bar containing about 0.02 wt.% of Ce compared to that of the standard production were not achieved. The wind power shaft with content of about 0.06 wt.% of Ce showed high amount of REM inclusions, which were locally chained, and in some cases, initiated cracks. Four stoichiometrically different types of REM inclusions were detected in forgings, namely (La-Ce)2O2S + (La-Ce)O2 + SiO2 (minority); oxygen, phosphorus, arsenic, and antimony bound to lanthanum and cerium probably bonded with iron oxides La + Ce, MgO, Al2O3 a SiO2; (La-Ce)2O2S, FeO, SiO2, and CaO or CaS.

The Effect of Laser Beam Processing on the Properties of WC-Co Coatings Deposited on Steel.

The main objective of the present work is to determine the effects of laser processing on properties of WC-Co electro-spark deposited (ESD) coatings on steel substrates. Tungsten carbide coatings have been applied to steel substrates using a manual electrode feeder, model EIL-8A. The laser beam processing (LBP) of electro-spark coatings was performed using an Nd:YAG fiber laser. The microstructure and properties of laser treated/melted coatings were evaluated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), surface geometric structure (SGS) and roughness measurements and adhesion, microhardness, residual stresses, corrosion resistance and application tests. The obtained experimental data were subjected to statistical analysis and multidimensional numerical and visual exploratory techniques. It has been shown conclusively that the laser-treated ESD WC-Co coatings are characterized by lower microhardness, higher resistance to corrosion, increased roughness and better adhesion to the substrate. LBP homogenizes the chemical composition, refines the microstructure and heals microcracks and pores of ESD coatings. The laser treated ESD WC-Co coatings can be used in frictional sliding nodes (e.g., on the front seal rings used in pumps) and as protective layers.

Inter-observer and intra-observer reliability in the radiographic measurements of paediatric forefoot alignment.

BACKGROUND: Foot bones in children have more rounded shapes in radiograms than adults. Thus, the goal of this work was assessing inter- and intra-observer reliability in paediatric forefoot angle measurements. MATERIAL AND METHODS: Six forefoot angles in 34 AP standing paediatric foot radiographs were measured by 5 researchers. A classic statistical analysis with use of IBM SPSS Statistics 25 was performed and a new method with two-way analysis of variance was applied. RESULTS: Results of statistical analysis revealed the properties of a subjective assessment related to specific angles. Kilmartin's angle, calcaneus-fifth metatarsal angle and first ray angle are the most reliable; metatarsus adductus angle should be used with great caution in pediatric population. Engel's angle is the most difficult for measuring and measurement error is the highest. CONCLUSION: The power of paediatric forefoot measurements is various. Several angles are reliable, while Engle's angle is the most doubtful.

The Morphology and Mechanical Properties of ESD Coatings before and after Laser Beam Machining.

Electro-spark deposition (ESD) and laser beam machining (LBM) are the technologies using the concentrated energy flux. This paper deals with the issue of the impact of laser modification on the morphology and mechanical properties of carbide/copper coatings produced by electro-spark treatment. The coatings were applied to C45 carbon steel samples using the EIL-8A device. The following three types of electrodes made using the powder metallurgy (PM) hot pressing technique, from copper and tungsten carbide powders of different percentage compositions, were used for the coatings: 25% WC and 75% Cu; 50% WC and 50% Cu; and 75% WC and 25% Cu. Laser modification of the surface layers was performed with an Nd:YAG laser. The research focused on the analysis of the morphology of coatings applied by electro-spark technology before and after laser processing. The analysis of the morphology of electro-spark coatings revealed that the coatings had microcracks and pores. The laser beam machining of ESD coatings led to the homogenization of chemical composition, fragmentation of the structure, and elimination of microcracks. In addition, measurements of porosity, microhardness, adhesion, and analysis of XRD phase composition of the electro-spark coatings were performed. Laser processing proved to have a positive effect on improving the adhesion of coatings and reducing their porosity. This paper also presents a simulation model of heat transfer processes for the case of laser radiation impact on a WC-Cu coating. The developed numerical model, describing the influence of laser treatment on the distribution of temperature fields in the heated material (at a given depth) is of significant importance in the development of treatment technologies. Laser-modified ESD coatings perform anti-wear and protective functions, which enable their potential application in means of transport such as rolling stock.

Elicitation with methyl jasmonate combined with cultivation in the Plantform™ temporary immersion bioreactor highly increases the accumulation of selected centellosides and phenolics in Centella asiatica (L.) Urban shoot culture.

Centella asiatica (L.) Urban is an important pharmacopoeial plant used not only in medicine but also in cosmetology. C. asiatica agitated shoot cultures were established to study the influence of ethephon, methyl jasmonate, l-phenylalanine (Eth 50 µM, MeJa 50 µM, L-Phe 2.4 g/L of medium, respectively; seven variants of the supplementation) on the accumulation of secondary metabolites: the main centellosides (asiaticoside and madecassoside) and selected phenolic acids, and flavonoids in the biomass. Microshoots were harvested two and six days after the supplementation. Secondary metabolites were analyzed in methanolic extracts by UPLC-MS/MS (centellosides) and by HPLC-DAD (phenolics). In comparison with the reference cultures, the concentrations of individual secondary metabolites increased as follows: centellosides up to 5.6-fold (asiaticoside), phenolic acids up to 122-fold (p-coumaric acid) and flavonoids up to 22.4-fold (kaempherol). The highest production increase of individual compounds was observed for different variants of supplementation. Variant C (50 µM MeJa), the most optimal for centellosides and flavonoid accumulation, was selected for the experiment with bioreactors. Bioreactor Plantform™, compared to RITA® system and agitated cultures, appeared to be the most advantageous for secondary metabolites production in C. asiatica shoot cultures. The phenolic acid, flavonoid, centelloside, and total secondary metabolite productivity in Plantform™ system is 1.8-fold, 1.7-fold, 2.8-fold, 2.1-fold, respectively, higher than in MeJa elicitated agitated cultures, and 4.3-fold, 7.3-fold, 12.2-fold, 7.2-fold, respectively, higher than in control agitated cultures.

Enhanced accumulation of harpagide and 8-O-acetyl-harpagide in Melittis melissophyllum L. agitated shoot cultures analyzed by UPLC-MS/MS.

Harpagide and its derivatives have valuable medicinal properties, such as anti-inflammatory, analgesic and potential antirheumatic effects. There is the demand for searching plant species containing these iridoids or developing biotechnological methods to obtain the compounds. The present study investigated the effects of methyl jasmonate (MeJa, 50 µM), ethephon (Eth, 50 µM) and L-phenylalanine (L-Phe, 2.4 g/L of medium), added to previously selected variant of Murashige and Skoog medium (supplemented with plant growth regulators: 6-benzylaminopurine 1.0 mg/L, α-naphthaleneacetic acid 0.5 mg/L, gibberellic acid 0.25 mg/L) on the accumulation of harpagide and 8-O-acetyl-harpagide in Melittis melissophyllum L. agitated shoot cultures. Plant material was harvested 2 and 8 days after the supplementation. Iridoids were quantitatively analyzed by the UPLC-MS/MS method in extracts from the biomass and the culture medium. It was found that all of the variants caused an increase in the accumulation of harpagide. In the biomass harvested after 2 days, the highest harpagide content of 247.3 mg/100 g DW was found for variant F (L-Phe and Eth), and the highest 8-O-acetyl-harpagide content of 138 mg/100 g DW for variant E (L-Phe and MeJa). After 8 days, in some variants, a portion of the metabolites was released into the culture medium. Considering the total amount of the compounds (in the biomass and medium), the highest accumulation of harpagide, amounting to 619 mg/100 g DW, was found in variant F, and the highest amount of 8-O-acetyl-harpagide, of 255.4 mg/100 g DW, was found in variant H (L-Phe, MeJa, Eth) when harvested on the 8th day. These amounts were, respectively, 24.7 and 4.8 times higher than in the control culture, and were, respectively, 15 and 6.7 times higher than in the leaves of the soil-grown plant. The total amount of the two iridoids was highest for variant F (0.78% DW) and variant H (0.68% DW) when harvested on the 8th day. The results indicate that the agitated shoot cultures of M. melissophyllum can be a rich source of harpagide and 8-O-acetyl-harpagide, having a potential practical application. To the best of our knowledge we present for the first time the results of the quantitative UPLC-MS/MS analysis of harpagide and 8-O-acetyl-harpagide in M. melissophyllum shoot cultures and the enhancement of their accumulation by means of medium supplementation with elicitors and precursor.

Enhanced production of the pharmaceutically important polyphenolic compounds in Vitex agnus castus L. shoot cultures by precursor feeding strategy.

Agitated Vitex agnus castus L. shoot cultures were established to analyse the content of selected pharmaceutically important flavonoids and phenolic acids. Two variants (selected from nine ones) of MS medium were prepared: A (BAP 1 mg/L; NAA 0.5 mg/L; GA3 0.25 mg/L) and B (BAP 2 mg/L; NAA 0.5 mg/L). The biomass was harvested after 1, 2, 3,4, 5 and 6 weeks. Four-week cultures (variant A) were selected to perform the precursor feeding experiment. The L-phenylalanine dose of 1.6 g/L appears to be the most advantageous. Compared to the control cultures, the content of the individual compounds increased in a range from 1.4 to 17.3-fold (e.g. p-coumaric acid - 17.3 fold; casticin - 4.8-fold). The biomass from in vitro cultures is richer in neochlorogenic acid (16-fold), p-coumaric acid (5.3-fold), rutin (2.8-fold), caffeic acid (1.5-fold) and cinaroside (1.5-fold) than the leaves of its parent greenhouse-cultivated plants. Extracts contained 30 mg/100 g DW of casticin, but after the hydrolysis its amount increased up to 200 mg/100 g DW and twice exceeded the content in the greenhouse leaves. The results indicate that V. agnus castus agitated shoot cultures might be considered as a potential biotechnological source of some pharmaceutically important compounds, especially casticin, rutin, neochlorogenic and p-coumaric acids.

Seasonal changes of flavonoid content in Melittis melissophyllum L. (Lamiaceae).

Melittis melissophyllum L., a medicinal plant currently used in the folk medicine, was analyzed for the content of flavonoid compounds. The plants were collected in two locations in Poland in May and September. MeOH Extracts from the leaves and flowers (separately) were analyzed by HPLC-DAD. Eight compounds were identified in all the samples and quantitatively analyzed as cinaroside (=luteolin 7-O-glucoside), rutin, myricetin, quercitrin, quercetin, luteolin, kaempferol, and apigenin. M. melissophyllum accumulated the highest total amounts of flavonoids in May (flowers: from 258 to 271 mg/100 g dry weight (dw); leaves: from 143 to 155 mg/100 g dw) and significantly lower ones in September (leaves: from 83 to 92 mg/100 g dw). The main compound was cinaroside (May: up to 249 mg/100 g dw; September: up to 43 mg/100 g dw). Advanced multivariate statistical techniques (cluster analysis (CA) and principal component analysis (PCA)) were used to characterize the sample populations and to analyze the data. We report, for the first time, the results of the quantitative analysis of M. melissophyllum flavonoids and seasonal changes in their accumulation. Our results show that the time of harvesting has a significant influence on the flavonoid content in M. melissophyllum, while the geographical location does not have such an effect.

The influence of L-phenylalanine, methyl jasmonate and sucrose concentration on the accumulation of phenolic acids in Exacum affine Balf. f. ex Regel shoot culture.

Phenolic acids are an important group of plant secondary metabolites with various, valuable therapeutic properties. Apart from plants growing in the open air, tissue cultures can be an alternative source of the secondary metabolites. The yield of their accumulation in in vitro cultures can be increased by different methods, including culture medium supplementation with precursors, elicitors and changing the standard amounts of the medium components. The purpose of this study was to investigate the influence of the precursor (L-phenylalanine), the elicitor (methyl jasmonate) and a higher sucrose concentration on the phenolic acids accumulation in the agitated shoot cultures of Exacum affine Balf. f. ex Regel (Gentianaceae). Qualitative and quantitative analyses of the phenolic acids in methanolic extracts from the biomass were conducted by applying the HPLC method. Fourteen phenolic acids and cinnamic acid were found in all samples. The total content of free phenolic acids increased from approximately 0.242% to 0.635% (2.6-fold) and the total content of the whole phenolic acids (free and bound) - from 0.712% to 1.160% (1.6-fold). The studies show that the best variant for the accumulation of most of the identified phenolic acids contained 6% of sucrose (double the standard amount), L-phenylalanine 1.6 gL(-1) of medium and methyl jasmonate 100 µM. The analysis of the results in the experiment presented here showed that it is possible to increase the accumulation of the phenolic acids in Exacum affine shoot cultures - by adding the precursor (L-phenylalanine), the elicitor (methyl jasmonate) and by increasing the sucrose concentration.

Chemical profile and seasonal variation of phenolic acid content in bastard balm (Melittis melissophyllum L., Lamiaceae).

Melittis melissophyllum L. is an old medicinal plant. Nowadays it is only used in the folk medicine but formerly it has been applied in the official medicine as a natural product described in French Pharmacopoeia. M. melissophyllum herbs used in our studies were collected from two localities in Poland in May and September. Methanolic plant extracts were purified by means of solid-phase extraction and then analysed by HPLC-DAD for their phenolic acid profile. Eleven compounds were identified in all plant samples and quantitatively analysed as: protocatechuic, chlorogenic, p-hydroxybenzoic, vanillic, caffeic, syringic, p-coumaric, ferulic, sinapic, o-coumaric and cinnamic acid. Plant materials contained free and bound phenolic acids. The main compounds were: p-hydroxybenzoic acid (30.21-54.16 mg/100 g dw and 37.04-56.75 mg/100 g dw, free and bound, respectively) and p-coumaric acid (40.48-80.55 mg/100 g dw and 28.09-40.85 mg/100 g dw, free and bound, respectively). The highest amounts of the investigated compounds were found in all samples collected in September, e.g. p-hydroxybenzoic acid (September 51.72-54.16 mg/100 g dw vs. May 30.21-34.07 mg/100 g dw), p-coumaric acid (September 77.14-80.55 mg/100 g dw vs. May 40.48-43.2 5mg/100 g dw). Multivariate statistical and data mining techniques, such as cluster analysis (CA) and principal component analysis (PCA), were used to characterize the sample populations according to the geographical localities, vegetation period and compound form (free or bound). To the best of our knowledge we report for the first time the results of quantitative analysis of M. melissophyllum phenolic acids and seasonal variation of their content. Plant herbs are usually collected at flowering for plant derived medical preparations. Our results show that it is not always the optimal time for the highest contents of active compounds.