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Novel tetrakis lanthanide beta-diketonate complexes: Structural study, luminescence properties and temperature sensing
No full textIn this study, we report the synthesis and some new crystal structures of tetrakis lanthanide beta-diketonate complexes throughout the lanthanide series for homonuclear (Pr3+ Nd3+, Sm3+, Eu3+, Tb3+, Dy3+, Er3+ and Yb3+) as well as for heteronuclear (Eu3+ -Tb3+ and Tb3+ -Sm3+) complexes. The well-known 1,1,1-trifluoro-2,4-pentadione (Htfac) ligand has been used in the synthesis. Here, we show that when employing the same synthesis conditions, we can obtain complexes with different coordination environments of the lanthanide ions. This is strongly linked to the ionic radius of the lanthanide ion. The luminescence properties of the visible emitting complexes (Ln(3+) = Eu3+, Tb3+, Sm3+ and Dy3+) were investigated in solution as well as solid state. The near- infrared emitting complexes (Ln(3+) = Pr3+, Nd3+,Er3+ and Yb3+) were recorded in the solid state. The heteronuclear complexes (IEu1-xTbx(tfac)(8) ]Na-2-(2)+ (x: 0.59 (1) and 0.47 (2), Tb1-ySmy (tfac)(8)]Na-2-(2)+ (y: 0.1 (3) and 0.2 (4)) and homonuclear complex [Dy(tfac)(4))] (DyL4) exhibited temperature-dependent luminescence properties in the physiological range, with complex DyL4 showing the highest relative sensitivity S-r = 3.45% K-1 (280 K). Complex 2 also showed a high S-r = 2.70% K-1 (353 K), which makes them promising for application as physiological luminescence thermometers. To the best of our knowledge until now no lanthanide beta-diketonate complexes have been reported for use as good luminescence thermometers operating in the physiological range
The effect of storage temperature and water activity on aflatoxin B-1 accumulation in hull-less and hulled spelt grains
No full textBACKGROUNDIn concomitance with shifts in climate conditions in recent years, an increasingly frequent emergence of Aspergillus flavus and aflatoxins in cereals has been observed. In this study the effects of temperature (15, 23, 30 and 37 degrees C) and water activity (a(w)) (0.85, 0.90, 0.95 and 0.99) on aflatoxin B-1 (AFB(1)) production by A. flavus isolate inoculated on hull-less and hulled spelt grains were investigated. RESULTSThe optimal conditions for AFB(1) biosynthesis were reached at 30 degrees C and a(w) value of 0.99 in the all tested samples (hull-less grains, dehulled spelt grains and hulls). The AFB(1) accumulation was significantly higher in hull-less than in dehulled grains, that implicated a protective effect of spelt hulls. The levels of AFB(1) were about 10-170 times higher in hulls than in grains. In order to determine the possibility of predicting the occurrence of AFB(1) under different storage conditions mathematical models [second order polynomial (SOP) and artificial neural network (ANN)] were applied. CONCLUSIONThe achievement of such estimation facilitates further decisions on continuous monitoring of the potential hazard related to AFB(1) contamination of stored spelt-based food. The knowledge of the storage temperature and a(w) effects on the AFB(1) content in spelt during the postharvest phase is of great practical importance
Thermal behaviour and degradation kinetics of apple pomace flours
No full textUsing differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) thermal characteristics and degradation kinetic parameters of apple pomace flours (APF1-5), obtained by dehydration of apple pomace (originating from single and mixed apple varieties, grown both organically and conventionally) and ground to particle size below of 300 mu m, were determined. Glass transition (T-g) close to common storage temperature (21 degrees C) was ascribed to commercial sample and T-g well above it (28-38 degrees C) to APF1-5. Both values of T-g and low water activity (0.2-0.4) prolong APF shelf-life. The kinetic parameters of the thermal degradation process: activation energy (E) in the range from 83 to118 kJ/mol, logarithmic value of pre-exponential factor (ln(A/min(-)1)) in the range from 20 to 28, and rate constant (k(200)) from 0.143 to 0.278 min(-1) were calculated. APF samples were grouped according to rate constant (k(200)) values of thermal degradation process at baking temperature (200 degrees C). Organic samples were found to have a higher thermal stability
Physicochemical properties and mineral content of honey samples from Vojvodina (Republic of Serbia)
No full textForty-five honey samples of three honey types - two monofloral (acacia and sunflower) and one polyfloral (meadow) were collected from the Autonomous Province of Vojvodina (Republic of Serbia) and analysed for their physicochemical parameters (moisture, acidity, pH, ash, electrical conductivity, glucose, fructose, hydroxymethylfurfural (HMF), CIE L*a*b* colour and mineral content). All tested physicochemical parameters were in agreement with the EU regulation except for moisture (4 samples) and HMF content (1 sample). Principal component analysis (PCA) was used for assessing the effects of three honey types on all investigated physicochemical parameters. According to PCA, acacia honey samples can be clearly isolated and form a cluster, while, regarding other honey types, PCA can offer the possibility to distinguish sunflower and meadow honey samples regarding examined physicochemical parameters and mineral content
Prevalence, knowledge and attitudes towards using sports supplements among young athletes
No full textBackgroundThe aim of this international study was to investigate the prevalence of the use of sports supplements among young athletes, as well as their knowledge and attitudes towards sports supplementation.MethodsOrganized survey study testing the level of knowledge, attitudes, beliefs and practices concerning the use of sports supplements was administered to 348 athletes, 15-18year olds from 4 countries competing in 18 sports at the international level.ResultsThe prevalence rate of the intake of sports supplements was 82.2%, with the protein supplements being predominant (54.5%). Coaches were identified as the primary source of information regarding supplementation (41.4%). The enhancement of athletic performance (35.4%) was the major motivation for the supplements intake. The majority of athletes (72.1%) were aware of associated health risks. The young athletes possess varying levels of knowledge regarding their own supplementation. The obtained data about the level of knowledge were statistically analyzed using the correspondence analysis. Less than 40% of athletes had the knowledge about the proper and intended use of protein, creatine, amino acids, beta alanine and glutamine, while they had greater understanding about vitamins and minerals, sports drinks and caffeine. The athletes in developed countries had greater access and utilization of professional resources such as dieticians. Young athletes are still unfamiliar with WADA regulations (55.5%), and the misuse of sports supplements represents an ethical dilemma for some.ConclusionThese findings indicate the necessity of a comprehensive education of all team members about sports supplements and careful supervision of the athletic development of young athletes
Solution-processable Yb/Er 2D-layered metallorganic frameworks with high NIR-emission quantum yields
No full textHere we report on solution-processable homo- and hetero-metallic Yb3+, Er3+ and Gd3+ lanthanide 2D-layered metallorganic frameworks with the chlorocyananilate linker (ClCNAn(2-), the dianion of 2-chloro-5-cyano-3,6-dihydroxybenzoquinone) showing long-lived emission in the near-infrared (NIR) spectral region after efficient ligand photosensitization. In these compounds the nature of the lanthanide ion determines the in-plane structural arrangement of the 2D layers, giving rise to peculiar porous networks. The investigated compounds, which are synthesized in high yields through a rapid one-pot procedure, show strong luminescence upon ligand excitation in a broad visible range with unusually long-lived emission for Er3+ (similar to 10 mu s), either in the bulk crystalline state, in solution, or in crystalline films dropcast from solution. The remarkable sensitization properties of the ligand provide NIR emission total quantum yields as high as 15.6% for Yb3+ and 0.16% for Er3+ in DMSO-d(6), which are the highest so far reported for coordination compounds. Efficient Yb-to-Er energy transfer is observed in the heterometallic derivative, which is maintained in all the studied material phases. The remarkable optical performance, the high thermal stability, the facile synthesis and the suitability for solution processing make these materials particularly promising for integration in photonic devices working in the NIR
Multiobjective process optimization for betaine enriched spelt flour based extrudates
No full textThe main purposes of this work are successful modeling of twin-screw extrusion process using predictive models, investigating the effect of process parameters such as screw speed, feed rate, and feed moisture content on the process and product responses and finally optimizing the process regarding betaine content in the extruded product and energy consumption. The second order polynomial approximation models and the artificial neural network were developed to predict the betaine content, showing the high accuracy in the prediction of experimental results. This study introduces the multiobjective optimization (MOO) approach in the extrusion process of spelt flour. The maximal betaine content (between 1,506.8 and 1,605.2 mg/40 g) and minimal energy consumption (between 101.3 and 108.5 W hr/kg) were indicated by MOO procedure, which were gained using the following input parameters: feed flow rate feed about 24 kg/h, screw speed about 252 RPM and moisture content from 21.6 to 23.4%
Synthesis and luminescence properties of a novel dazzling red-emitting phosphor NaSr3SbO6:Mn4+ for UV/n-UV w-LEDs
No full textIn this paper, a novel kind of tristrontium sodium antimony(V) oxide (NaSr3SbO6: Mn4+; NSSO: Mn4+) material was developed, whose crystal structure is different from the well-researched Mn4+-doped antimoniate double pervoskite materials. The optimal NSSO: 0.006Mn(4+) can be mainly excited using ultraviolet/nearultraviolet (UV/n-UV) and partial blue lights with a high quantum yield of 46% upon 365 nm UV excitation and good temperature dependent performance
Laser treatments of nimonic 263 nickel-based superalloy [laserske obrade superlegure nimonik 263]
No full textIn this paper, the influence of parameters of laser processing (drilling, cutting, welding and laser shock peening) on microstructure of superalloy Nimonic 263 are investigated. Drilling and welding process are carried out on the Nd: YAG laser model LS-HTS Mobile P160. When drilling the holes, the parameters of pulse frequency (5 Hz, 7 Hz and 9 Hz) and the pulses duration (1.8 ms to 3.6 ms) are varied. The microstructure is investigated and geometrical and metallurgical characteristics of the holes are determined.Cutting is carried out on the laser BISTRONIC, (2000), BISTAR 3015. The parameters that were varied are as follows: the average laser power, laser velocity, the pressure of the assisting gas and the focus position. Based on the geometrical characteristics of the cuts and surface morphology the optimal parameters are discussed and defined. The laser welded joints of Nimonic 263, in addition to microscopic examination and surface profilometry, were subjected to the destructive testing. During the laser shock peening, the samples were exposed to laser light at a wavelength of 1064 nm and 532 nm, with the number of accumulated pulses 50, 100 and 200. The operating laser was Nd: YAG EKSPLO, SL212P model. Structural analysis of Nimonic 263 was carried out using light microscopy, scanning electron microscopy and EDS analysis. Microhardness measurements were carried out using the Vickers method under load of 9,81N. Profilometry was performed on a contactless profilometer Zygo Newview 7100