Um die anderen Arten von Veröffentlichungen zu diesem Thema anzuzeigen, folgen Sie diesem Link: Fourier trans-formation.
Zeitschriftenartikel zum Thema „Fourier trans-formation“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Machen Sie sich mit Top-18 Zeitschriftenartikel für die Forschung zum Thema "Fourier trans-formation" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Sehen Sie die Zeitschriftenartikel für verschiedene Spezialgebieten durch und erstellen Sie Ihre Bibliographie auf korrekte Weise.
1
Johnson, W. C., und B. J. Lyons. „Radiolytic formation and decay of trans-vinylene unsaturation in polyethylene: Fourier transform infra-red measurements“. Radiation Physics and Chemistry 46, Nr. 4-6 (Oktober 1995): 829–32. http://dx.doi.org/10.1016/0969-806x(95)00271-x.
Der volle Inhalt der Quelle
2
Ortega, Jose, Arturo Martínez Zavala, Maribel Hernández und Joel Díaz Reyes. „Analysis of trans fatty acids production and squalene variation during amaranth oil extraction“. Open Chemistry 10, Nr. 6 (01.12.2012): 1773–78. http://dx.doi.org/10.2478/s11532-012-0104-4.
Der volle Inhalt der QuelleAnnotation:
AbstractThe purpose of this study was to evaluate the decay of squalene and the formation of trans fatty acids (TFAs) in the amaranth oil extracted with hexane with and without heat. Oils were analyzed by determining their chemical values, and the fatty acids were identified and quantified by using Fourier-transform infrared (FTIR) spectroscopy, in the mid-region of 400–4000 cm−1, and gas chromatography. The FTIR analysis shows that two oil extracts (with and without heat) present a well-defined peak at 968 cm−1, which represents the trans double bonds. The quantified TFAs are
3
Antiñolo, María, María Asensio, José Albaladejo und Elena Jiménez. „Gas-Phase Reaction of trans-2-Methyl-2-butenal with Cl: Kinetics, Gaseous Products, and SOA Formation“. Atmosphere 11, Nr. 7 (05.07.2020): 715. http://dx.doi.org/10.3390/atmos11070715.
Der volle Inhalt der QuelleAnnotation:
The gas-phase reaction between trans-2-methyl-2-butenal and chlorine (Cl) atoms has been studied in a simulation chamber at 298 ± 2 K and 760 ± 5 Torr of air under free-NOx conditions. The rate coefficient of this reaction was determined as k = (2.45 ± 0.32) × 10−10 cm3 molecule−1 s−1 by using a relative method and Fourier transform infrared spectroscopy. In addition to this technique, gas chromatography coupled to mass spectrometry and proton transfer time-of-flight mass spectrometry were used to detect and monitor the time evolution of the gas-phase reaction products. The major primary reaction product from the addition of Cl to the C-3 of trans-2-methyl-2-butenal was 3-chloro-2-butanone, with a molar yield (YProd) of (52.5 ± 7.3)%. Acetaldehyde (Y = (40.8 ± 0.6)%) and HCl were also identified, indicating that the H-abstraction by Cl from the aldehyde group is a reaction pathway as well. Secondary organic aerosol (SOA) formation was investigated by using a fast mobility particle sizer spectrometer. The SOA yield in the Cl + trans-2-methyl-2-butenal reaction is reported to be lower than 2.4%, thus its impact can be considered negligible. The atmospheric importance of the titled reaction is similar to the corresponding OH reaction in areas with high Cl concentration.
4
García-González, Diego L., und Frederik R. Van De Voort. „A Novel Wire Mesh “Cell” for Studying Lipid Oxidative Processes by Fourier Transform Infrared Spectroscopy“. Applied Spectroscopy 63, Nr. 5 (Mai 2009): 518–27. http://dx.doi.org/10.1366/000370209788346995.
Der volle Inhalt der QuelleAnnotation:
A novel infrared (IR) sample handling accessory has been developed to monitor and study oxidation processes of edible oils under moderate temperature conditions by Fourier transform infrared (FT-IR) spectroscopy. A reusable stainless steel mesh IR “cell” was designed and evaluated from the standpoint of mesh size, transmission characteristics, its ability to entrap oil, and techniques to apply sample and normalize path length so as to obtain good quality, reproducible spectra. The concept is to entrap oil within the mesh by means of its inherent surface tension and to take advantage of the high surface area provided by the mesh to facilitate rapid oxidation of the oil by air at ambient or slightly elevated temperatures without having to resort to more extreme temperature conditions to track oxidative changes in real time. Changes taking place in canola oil at room temperature, in the dark and exposed to light, as well as at 50 °C are presented to illustrate the performance of the cell in monitoring oxidative changes in real time (e.g., formation of hydroperoxides, loss of cis and formation of trans double bonds). The mesh cell should be useful for comparing the relative performance of antioxidants as well as evaluating the oxidative stability of oils, among other applications.
5
Clark, Peter D., James F. Fait, Colin G. Jones und Martin J. Kirk. „Reactions of benzo[b]thiophene with some aqueous platinum metal species at elevated temperatures“. Canadian Journal of Chemistry 69, Nr. 4 (01.04.1991): 590–98. http://dx.doi.org/10.1139/v91-089.
Der volle Inhalt der QuelleAnnotation:
The desulfurization of benzo[b]thiophene 1 with aqueous transition metal species in the presence of various hydrocarbons at elevated temperatures is described. Mechanistic studies have shown that treatment of 1 with solutions of RuCl3 and other platinum metal species results in the formation of 2,3-dihydrobenzo[b]thiophene 2 and ethylbenzene 3 as major products. Metal coordinated species are probable intermediates in the formation of 2 and hydrocarbon products. 2 readily coordinates to PdCl2 to form square-planar trans-dichlorobis(2,3-dihydrobenzo[b]thiophene) palladium(II), which decomposes to ethylbenzene at 300 °C. The crystal structure of the complex was determined by a single crystal X-ray diffraction study. The complex crystallized in the monoclinic space group C 2/c with Z = 8 in a cell of dimensions a = 23.057 (3), b = 9.711 (1), c = 15.227 (2) Å and β = 99.74(1)°. The structure was solved by the Fourier method and was refined by full-matrix least-squares calculations to R = 0.042 for 2537 observed data with I > 2.5σ(I). Key words: benzo[b]thiophene, desulfurization, platinum metal species.
6
RATH, Parshuram, Frank DELANGE, J. Willem DEGRIP und J. Kenneth ROTHSCHILD. „Hydrogen bonding changes of internal water molecules in rhodopsin during metarhodopsin I and metarhodopsin II formation“. Biochemical Journal 329, Nr. 3 (01.02.1998): 713–17. http://dx.doi.org/10.1042/bj3290713.
Der volle Inhalt der QuelleAnnotation:
Rhodopsin is a 7-helix, integral membrane protein found in the rod outer segments, which serves as the light receptor in vision. Light absorption by the retinylidene chromophore of rhodopsin triggers an 11-cis → all-trans isomerization, followed by a series of protein conformational changes, which culminate in the binding and activation of the G-protein transducin by the metarhodopsin II (Meta II) intermediate. Fourier transform IR difference spectroscopy has been used to investigate the structural changes that water, as well as other OH- and NH-containing groups, undergo during the formation of the metarhodopsin I (Meta I) and Meta II intermediates. Bands associated with the OH stretch modes of water are identified by characteristic downshifts upon substitution of H218O for H2O. Compared with earlier work, several negative bands associated with water molecules in unphotolysed rhodopsin were detected, which shift to lower frequencies upon formation of the Meta I and Meta II intermediates. These data indicate that at least one water molecule undergoes an increase in hydrogen bonding upon formation of the Meta I intermediate, while at least one other increases its hydrogen bonding during Meta II formation. Amino acid residue Asp-83, which undergoes a change in its hydrogen bonding during Meta II formation, does not appear to interact with any of the structurally active water molecules. Several NH and/or OH groups, which are inaccessible to hydrogen/deuterium exchange, also undergo alterations during Meta I and Meta II formation.
7
Miao, Xuepei, An Xing, Lifan He, Yan Meng und Xiaoyu Li. „One-Step Preparation of Hyperbranched Polyether Functionalized Graphene Oxide for Improved Corrosion Resistance of Epoxy Coatings“. Coatings 9, Nr. 12 (10.12.2019): 844. http://dx.doi.org/10.3390/coatings9120844.
Der volle Inhalt der QuelleAnnotation:
In this paper, hyperbranched polyether functionalized graphene oxide (EHBPE-GO) was prepared by a facile one-step method. Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), thermogravimetric analyzer (TGA), and trans-mission electron microscopy (TEM) results confirmed the formation of EHBPE-GO. Then, EHBPE-GO was cured with phenolic amides at room temperature to prepare epoxy coatings. The corrosion resistance of epoxy coatings was investigated systematically by using electrochemical and traditional immersion methods. Results show that a small amount of EHBPE-GO (8 wt % of Diglycidyl ether of bisphenol A (DGEBA)) in epoxy coating achieves 50% higher improvement in acid-resistance than unmodified neat DGEBA resin. For the nanocomposite epoxy coating, the superior acid-resistance is attributed to the increased crosslink density and the impermeable 2D structure of EHBPE-GO. This work provides a facile strategy to develop the effective improved corrosion resistance nanofiller for epoxy coating.
8
Horn, Michael, Karin Nienhaus und Gerd Ulrich Nienhaus. „Fourier transform infrared spectroscopy study of ligand photodissociation and migration in inducible nitric oxide synthase“. F1000Research 3 (28.11.2014): 290. http://dx.doi.org/10.12688/f1000research.5836.1.
Der volle Inhalt der QuelleAnnotation:
Inducible nitric oxide synthase (iNOS) is a homodimeric heme enzyme that catalyzes the formation of nitric oxide (NO) from dioxygen and L-arginine (L-Arg) in a two-step process. The produced NO can either diffuse out of the heme pocket into the surroundings or it can rebind to the heme iron and inhibit enzyme action. Here we have employed Fourier transform infrared (FTIR) photolysis difference spectroscopy at cryogenic temperatures, using the carbon monoxide (CO) and NO stretching bands as local probes of the active site of iNOS. Characteristic changes were observed in the spectra of the heme-bound ligands upon binding of the cofactors. Unlike photolyzed CO, which becomes trapped in well-defined orientations, as indicated by sharp photoproduct bands, photoproduct bands of NO photodissociated from the ferric heme iron were not visible, indicating that NO does not reside in the protein interior in a well-defined location or orientation. This may be favorable for NO release from the enzyme during catalysis because it reduces self-inhibition. Moreover, we used temperature derivative spectroscopy (TDS) with FTIR monitoring to explore the dynamics of NO and carbon monoxide (CO) inside iNOS after photodissociation at cryogenic temperatures. Only a single kinetic photoproduct state was revealed, but no secondary docking sites as in hemoglobins. Interestingly, we observed that intense illumination of six-coordinate ferrous iNOSoxy-NO ruptures the bond between the heme iron and the proximal thiolate to yield five-coordinate ferric iNOSoxy-NO, demonstrating the strong trans effect of the heme-bound NO.
9
Horn, Michael, Karin Nienhaus und Gerd Ulrich Nienhaus. „Fourier transform infrared spectroscopy study of ligand photodissociation and migration in inducible nitric oxide synthase“. F1000Research 3 (12.12.2014): 290. http://dx.doi.org/10.12688/f1000research.5836.2.
Der volle Inhalt der QuelleAnnotation:
Inducible nitric oxide synthase (iNOS) is a homodimeric heme enzyme that catalyzes the formation of nitric oxide (NO) from dioxygen and L-arginine (L-Arg) in a two-step process. The produced NO can either diffuse out of the heme pocket into the surroundings or it can rebind to the heme iron and inhibit enzyme action. Here we have employed Fourier transform infrared (FTIR) photolysis difference spectroscopy at cryogenic temperatures, using the carbon monoxide (CO) and NO stretching bands as local probes of the active site of iNOS. Characteristic changes were observed in the spectra of the heme-bound ligands upon binding of the cofactors. Unlike photolyzed CO, which becomes trapped in well-defined orientations, as indicated by sharp photoproduct bands, photoproduct bands of NO photodissociated from the ferric heme iron were not visible, indicating that NO does not reside in the protein interior in a well-defined location or orientation. This may be favorable for NO release from the enzyme during catalysis because it reduces self-inhibition. Moreover, we used temperature derivative spectroscopy (TDS) with FTIR monitoring to explore the dynamics of NO and carbon monoxide (CO) inside iNOS after photodissociation at cryogenic temperatures. Only a single kinetic photoproduct state was revealed, but no secondary docking sites as in hemoglobins. Interestingly, we observed that intense illumination of six-coordinate ferrous iNOSoxy-NO ruptures the bond between the heme iron and the proximal thiolate to yield five-coordinate ferric iNOSoxy-NO, demonstrating the strong trans effect of the heme-bound NO.
10
Suaniti, Ni Made, I. Wayan Bandem Adnyana und Tjokorda Gde Tirta Nindhia. „Ester Group Detection of Biodiesel from Used Cooking Oil with Sulphuric and Toluene Sulphuric Acid Catalysts“. Key Engineering Materials 877 (Februar 2021): 153–59. http://dx.doi.org/10.4028/www.scientific.net/kem.877.153.
Der volle Inhalt der QuelleAnnotation:
Used cooking oil is potential as raw material to produce biodiesel. We discovered fatty acid ethyl esters (FAEEs) and methyl esters (FAMEs) as biodiesel content indicator from esterification and trans-esterification reactions of used cooking oil with sulphuric acid and toluene sulphuric acid as catalysts. The purpose of this study was to examine some characteristics of FAEE and FAME synthesis from used cooking oil. The FAEEs and FAMEs were detected by separation in thin layer chromatography (TLC) and Fourier Transform Infrared (FT-IR) and compared to laurate standar. The used cooking oil was produced after frying of meat chicken for seven hours in a household. The Retardation Factor (Rf) of TLC of FAME of methyl laurate was 0.36 and FAEE of ethyl laurate was 0.23. The wavenumber indicating specific functional group of =CH was 3392 cm-1, while of alcohol as ester compound was 1739.79 cm-1. The wavenumber of C-C and CO groups were 1635.64 cm-1 and 1165 cm-1, respectively. These indicate the ester group in used cooking oil, which reflects the formation of bio-diesel.
11
Catenacci, Laura, Milena Sorrenti, Maria Cristina Bonferoni, Lee Hunt und Mino R. Caira. „Inclusion of the Phytoalexin trans-Resveratrol in Native Cyclodextrins: A Thermal, Spectroscopic, and X-Ray Structural Study“. Molecules 25, Nr. 4 (24.02.2020): 998. http://dx.doi.org/10.3390/molecules25040998.
Der volle Inhalt der QuelleAnnotation:
The aim of the study was to determine the feasibility of complexation between the antioxidant trans-resveratrol (RSV) and underivatized cyclodextrins (CDs) using a variety of preparative methods, including physical mixing, kneading, microwave irradiation, co-evaporation, and co-precipitation techniques. Products were characterized using differential scanning calorimetry (DSC), simultaneous thermogravimetric/DSC analysis (TGA/DSC), Fourier transform infrared (FT-IR) spectroscopy, and powder X-ray diffraction (PXRD). With α-CD and RSV, sample amorphization was revealed by PXRD and FT-IR, but no definitive inclusion complexation was evident. Similar results were obtained in attempts to complex RSV with β-CD. However, complex formation between γ-CD and RSV was evident from observation of an endo-/exothermic effect appearing in the DSC trace of the product from kneading and was further corroborated by FT-IR and PXRD methods. The latter technique indicated complexation unequivocally as the diffraction peak profile for the product matched that for known isostructural γ-CD complexes. Single crystal X-ray analysis followed, confirming the predicted complex between γ-CD and RSV. A combination of 1H NMR and TGA data yielded the complex formula (γ-CD)3·(RSV)4·(H2O)62. However, severe disorder of the RSV molecules prevented their modeling. In contrast, our previous studies of the inclusion of RSV in methylated CDs yielded crystals with only minor guest disorder.
12
Hiendrawan, Stevanus, Bambang Veriansyah und Raymond R. Tjandrawinata. „SOLID-STATE PROPERTIES AND SOLUBILITY STUDIES OF NOVEL PHARMACEUTICAL COCRYSTAL OF ITRACONAZOLE“. International Journal of Applied Pharmaceutics 10, Nr. 5 (08.09.2018): 97. http://dx.doi.org/10.22159/ijap.2018v10i5.26663.
Der volle Inhalt der QuelleAnnotation:
Objective: Pharmaceutical cocrystal is a promising method to improve the solubility of active pharmaceutical ingredients (APIs). Itraconazole (ITZ) is a BCS class II antifungal drug with poor aqueous solubility, therefore an attempt was made to improve the solubility of ITZ using cocrystallization technique. In this work, six novel pharmaceutical cocrystals of ITZ with various coformers, including 4-hydroxybenzoic acid (4HBA), trans-cinnamic acid (TCA), suberic acid (SUB), sebacic acid (SBC), 1-hydroxy-2-naphthoic acid (1H2N), and benzamide (BZD) were prepared.Methods: ITZ cocrystals was prepared by solvent evaporation process. The cocrystals produced were characterized using powder x-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and fourier transform infrared (FTIR) spectroscopy. Solubility analysis was performed to evaluate the cocrystals.Results: PXRD and DSC analysis revealed that the pattern of all ITZ cocrystals was distinguishable from the individual compounds which indicates the formation of new phase. The solubility of ITZ and its cocrystals from highest to lowest after 24 h in 0.1 N HCl solution (pH 1.2) follows the order ITZ-TCA (1.97-fold), ITZ-SBC (1.09-fold), ITZ, ITZ-1H2N (0.58-fold) and ITZ-4HBA (0.46-fold).Conclusion: This study demonstrates that the selection of coformers has pronounced an impact on the physicochemical properties of ITZ. Based on this study, it can be concluded that cocrystallization offers a valuable way to improve the solubility of ITZ.
13
Mojumdar, Enamul Haque, Lone Bruhn Madsen, Henri Hansson, Ida Taavoniku, Klaus Kristensen, Christina Persson, Anna Karin Morén et al. „Probing Skin Barrier Recovery on Molecular Level Following Acute Wounds: An In Vivo/Ex Vivo Study on Pigs“. Biomedicines 9, Nr. 4 (31.03.2021): 360. http://dx.doi.org/10.3390/biomedicines9040360.
Der volle Inhalt der QuelleAnnotation:
Proper skin barrier function is paramount for our survival, and, suffering injury, there is an acute need to restore the lost barrier and prevent development of a chronic wound. We hypothesize that rapid wound closure is more important than immediate perfection of the barrier, whereas specific treatment may facilitate perfection. The aim of the current project was therefore to evaluate the quality of restored tissue down to the molecular level. We used Göttingen minipigs with a multi-technique approach correlating wound healing progression in vivo over three weeks, monitored by classical methods (e.g., histology, trans-epidermal water loss (TEWL), pH) and subsequent physicochemical characterization of barrier recovery (i.e., small and wide-angle X-ray diffraction (SWAXD), polarization transfer solid-state NMR (PTssNMR), dynamic vapor sorption (DVS), Fourier transform infrared (FTIR)), providing a unique insight into molecular aspects of healing. We conclude that although acute wounds sealed within two weeks as expected, molecular investigation of stratum corneum (SC) revealed a poorly developed keratin organization and deviations in lipid lamellae formation. A higher lipid fluidity was also observed in regenerated tissue. This may have been due to incomplete lipid conversion during barrier recovery as glycosphingolipids, normally not present in SC, were indicated by infrared FTIR spectroscopy. Evidently, a molecular approach to skin barrier recovery could be a valuable tool in future development of products targeting wound healing.
14
Lopez, T., J. Hernandez-Ventura, D. H. Aguilar und P. Quintana. „Thermal Phase Stability and Catalytic Properties of Nanostructured TiO2-MgO Sol–Gel Mixed Oxides“. Journal of Nanoscience and Nanotechnology 8, Nr. 12 (01.12.2008): 6608–17. http://dx.doi.org/10.1166/jnn.2008.18434.
Der volle Inhalt der QuelleAnnotation:
Several compositions in the system TiO2-MgO were prepared via sol–gel method. The structural evolution of the samples was followed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermal analysis (DTA/TG). In order to study the crystalline phase stability over time, the amorphous fresh gels were subjected to successive thermal treatments from 100 to 1100 °C, with a total annealing time of 442 h. Below 350 °C, magnesium acetates and oxalates phases were detected; at higher temperatures the binary compounds MgTi2O5, MgTiO3 and Mg2TiO4 appeared over a wide range of compositions. In the titania rich end, brookite, anatase and rutile were detected, these phases easily reacted to form the binary oxides; in contrast, on the rich-end magnesia, periclase showed an overall high stability. The successive thermal treatments over an extended period of time allowed a better control of nanosized crystallite growth; for anatase was 30 nm, below 850 °C, and for rutile was 45 nm, between 600 °C and 1000 °C. Magnesia showed a constant value of 22 nm on the overall studied temperatures. The best catalytic performance for 2-propanol decomposition was achieved by 90Ti/10Mg, annealed at 400 °C; this indicates that when magnesium is added to titania, the catalytic activity improves due to the introduction of structural defects and charge deficiencies. For 2-butanol decomposition, the formation of cis and trans isomers indicates the presence of high acidity sites.
15
Witt, Matthias, und Hans-Friedrich Grützmacher. „Effects of Internal Hydrogen Bonds between Amide Groups: Gas-Phase Basicity and Proton Affinity of Linear Aliphatic Dicarboxamides“. European Journal of Mass Spectrometry 6, Nr. 2 (April 2000): 97–107. http://dx.doi.org/10.1255/ejms.317.
Der volle Inhalt der QuelleAnnotation:
The apparent gas-phase basicity GBapp and the proton affinity PA of aliphatic dicarboxamides has been determined by tandem mass spectrometry using the kinetic method. The diamides analyzed are primary maleic acid diamide (1a), fumaric acid diamide (2a) and trans, trans-muconic acid diamide (3a) and the tertiary N,N,N‘,N’-tetramethyl derivatives 2b and 3b, which have an almost fixed relative orientation of the terminal amide groups because of the C–C double bond(s) in the carbon skeleton, and the 1,n-dicarboxamides of succinic acid (4a) and (4b), of glutaric acid (5a) and (5b), of adipinic acid (6a) and (6b) and of sebacinic acid (7a) and (7b) containing a flexible –(CH2) n chain with n = 2, 3, 4 and 8. Very large differences are observed for GBapp derived from the dissociation of proton-bound heterodimers either as metastable ions or by CID for all diamides which are expected to form an internal proton bridge between the carbonyl-O atoms of the terminal amide groups in the protonated species. These effects indicate considerable conformational changes of the diamides by protonation and entropic effects accompanying the dissociation of their proton-bound heterodimers. To study the effect of collisional activation, which is believed to alter the effective temperature, Teff, of the proton-bound dimer ions, on their dissociation, separate experiments have been performed with thermalized proton bound heterodimers of 5a using Fourier transform ion cyclotron resonance (FT-ICR) spectrometry to control the collision energy. The evaluation of Teff from these experiments and the use of Teff in Van't Hoff plots to determine the PA of 5a shows a surprisingly good agreement with the results from tandem mass spectrometry, which supports the view that the kinetic method using different Teff can be used to determine the PA and the difference of the “apparent entropy” of protonation, Δ(Δ SH+) app, of the compound under study and the reference base of the proton bound heterodimer from GBapp even in the case of large entropy effects. The PA of maleic acid diamide 1a and its trans isomer 2a, not building an internal proton bridge by protonation, differ by 80 kJ mol−1. A value of −19 J mol−1 K is obtained for (Δ SH+) app (1a) while entropic effects are essentially absent in the case of 2a. The PA of linear dicarboxamides 4a–7a increases with the length of the –(CH2) n chain and exceeds that of monoamides of a comparable size by 60–100 kJ mol−1. This is attributed to the formation of an internal proton bridge and a release of constraints for the internal proton bridge for the longer chains. Δ(Δ SH+) app is practically constant for 5a–7a at a value of −41 ± 2 J mol−1 K, but only −19 J mol−1 K for 4a. This can be understood if the entropy loss during protonation of the diamides is mostly due to loss of internal rotations of the amide groups. In contrast to the primary amides, the tertiary dicarboxamides 4b–7b display identical PA independent of the length of the –(CH2) n chain, and the effect of formation of the internal proton bridge on the PA is distinctly less than for primary dicarboxamides. In addition, a constant value of only −16 ± 3 J mol−1 K is obtained for Δ(Δ SH+) app of 4b–7b. These results are interpreted by different types of the proton bridges of primary and tertiary diamides. Primary linear dicarboxamides generate a true proton bridge between the carbonyl-O atoms of the terminal amide groups as corroborated by ab initio calculations of their structures. In contrast, protonated tertiary dicarboxamides display properties of (internal) ion/dipole complexes in which the protonated amide group is “solvated” by the second one.
16
., Reham G. Elkomy. „Antimicrobial screening of silver nanoparticles synthesized by marine cyanobacterium Phormidium formosum“. Iranian Journal of Microbiology, 16.06.2020. http://dx.doi.org/10.18502/ijm.v12i3.3242.
Der volle Inhalt der QuelleAnnotation:
Background and Objectives: Nanoparticles are widely used in various fields such as electronics, cosmetics, water purifica- tion, biomedical and biotechnology. Biosynthesis of nanoparticles using biological agents have gained much attention in the area of nanotechnology in the last few decades because of cost effective, non-toxic, and eco-friendly. Algae have been used to reduce metal ions and subsequently for the biosynthesis of nanoparticles.
Materials and Methods: Silver nanoparticles (AgNPs) have been biosynthesized by Phormidium formosum isolated from Mediterranean Sea coast Egypt in an aqueous system. An aqueous solution of silver ions was treated with alive biomass of P. formousm for the formation of AgNPs. The physio-chemical properties of synthesized silver nanoparticles were studied using analytical techniques such as UV-Vis spectrophotometer, transmission electron microscopy (TEM), and Fourier Trans- form Infrared Spectroscopy (FTIR). The antimicrobial effect of synthesized silver nanoparticles was also tested on several microorganisms by measuring the inhibition zone.
Results: These nanoparticles showed an absorption peak at λmax 437 nm in the UV-visible spectrum, corresponding to the Surface Plasmon Resonance of AgNPs. The transmission electron micrographs of nanoparticles in an aqueous solution showed production of silver nanoparticles synthesized by P. formosum. The obtained AgNPs are spherical in shape with a size ranging from 1.83 nm to 26.15nm. The Fourier transmittance infrared spectrum (FTIR) confirms the presence of bio component in alive biomass of P. formosum which was responsible for the nanoparticles synthesis. The antimicrobial test revealed that AgNPs synthesized by P. formosum is capable to inhibit the growth of microorganisms.
Conclusion: The results confirmed that AgNPs can act as a powerful antimicrobial agent against fish and human pathogens.
17
Kumar, R., B. Bhattacharya, T. Agarwal und S. Chakkaravarthi. „Trans Fatty Acid Analysis of Frying Oil Using ATR-FTIR Spectroscopy: A Study on Indian Traditional Snack Foods“. Journal of Food Quality and Hazards Control, 30.05.2020. http://dx.doi.org/10.18502/jfqhc.7.2.2887.
Der volle Inhalt der QuelleAnnotation:
Background: Trans Fatty Acid (TFA) content in oil is an important quality parameter due to its adverse health effect. This study was aimed to examine the TFA content in the frying oil used by street food vendors in India for two traditional snack foods.
Methods: Totally, 143 oil samples were collected at different frying times (0, 2, and 4 h) from five different vendors for Samosa and Jalebi. TFA levels of the oil samples were analyzed by Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATRFTIR). Statistical analyses were carried out using SPSS software version 23.0.
Results: ATR-FTIR spectra exhibited an increase in peak intensity at 966 cm-1 with different frying time in both frying oil samples, indicating the formation of TFA. The TFA content in oils fried at 4 h was significantly higher than the ones at 0 and 2 intervals. It was found that 3 out of 74 (4%) Samosa fried oils and 12 out of 69 (17.4%) Jalebi fried oils were over the maximum allowed regulatory limit of TFA (5%). Jalebi fried oils had significantly higher TFA content than Samosa fried oils.
Conclusion: The increase in frying time decreased the peroxide values and increased saturated fatty acids and TFA values of oils used for both food items. The local vendors and consumers should be educated by national authorities regarding health risk of TFA in street fried snacks.
18
Chung, Chen-An, und Yuan-Pern Lee. „Infrared characterization of formation and resonance stabilization of the Criegee intermediate methyl vinyl ketone oxide“. Communications Chemistry 4, Nr. 1 (22.01.2021). http://dx.doi.org/10.1038/s42004-020-00447-1.
Der volle Inhalt der QuelleAnnotation:
AbstractMethyl vinyl ketone oxide (MVKO) is an important Criegee intermediate in the ozonolysis of isoprene. MVKO is resonance stabilized by its allyl moiety, but no spectral characterization of this stabilization was reported to date. In this study, we photolyzed a mixture of 1,3-diiodo-but-2-ene and O2 to produce MVKO and characterized the syn-trans-MVKO, and tentatively syn-cis-MVKO, with transient infrared spectra recorded using a step-scan Fourier-transform spectrometer. The O‒O stretching band at 948 cm−1 of syn-trans-MVKO is much greater than the corresponding bands of syn-CH3CHOO and (CH3)2COO Criegee intermediates at 871 and 887 cm−1, respectively, confirming a stronger O‒O bond due to resonance stabilization. We observed also iodoalkenyl radical C2H3C(CH3)I upon photolysis of the precursor to confirm the fission of the terminal allylic C‒I bond rather than the central vinylic C‒I bond of the precursor upon photolysis. At high pressure, the adduct C2H3C(CH3)IOO was also observed. The reaction mechanism is characterized.