Academic literature on the topic 'Fourier trans-formation'

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

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.

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.

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.

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.

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.

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.

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.

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.

Kryptografie je velmi důležitým aspektem našeho každodenního života, protože poskytuje teoretický základ informační bezpečnosti. Kvantové výpočty a informace se také stávají velmi důležitou oblastí vědy kvůli mnoha aplikačním oblastem včetně kryptologie a konkrétněji v kryptografii veřejných klíčů. Obtížnost čísel do hlavních faktorů je základem některých důležitých veřejných kryptosystémů, jejichž klíčem je kryptosystém RSA . Shorův kvantový faktoringový al-goritmus využívá zejména kvantový interferenční účinek kvantového výpočtu k faktorovým semi-prime číslům v polynomiálním čase na kvantovém počítači. Ačkoli kapacita současných kvantových počítačů vykonávat Shorův algoritmus je velmi omezená, existuje mnoho rozsáhlých základních vědeckých výzkumů o různých technikách optimalizace algoritmu, pokud jde o faktory, jako je počet qubitů, hloubka obvodu a počet bran. v této práci jsou diskutovány, analyzovány a porovnávány různé varianty Shorova factoringového algoritmu a kvantových obvodů. Některé varianty Shorova algoritmu jsou také simulované a skutečně prováděné na simulátorech a kvantových počítačích na platformě IBM QuantumExperience. Výsledky simulace jsou porovnávány z hlediska jejich složitosti a míry úspěšnosti. Organizace práce je následující: Kapitola 1 pojednává o některých klíčových historických výsledcích kvantové kryptografie, uvádí problém diskutovaný v této práci a představuje cíle, kterých má být dosaženo. Kapitola 2 shrnuje matematické základy kvantového výpočtu a kryptografie veřejných klíčů a popisuje notaci použitou v celé práci. To také vysvětluje, jak lze k rozbití kryptosystému RSA použít realizovatelný algoritmus pro vyhledávání objednávek nebo factoring. Kapitola 3 představuje stavební kameny Shorova algoritmu, včetně kvantové Fourierovy transformace, kvantového odhadu fází, modulární exponentiace a Shorova algoritmu. Zde jsou také uvedeny a porovnány různé varianty optimalizace kvantových obvodů. Kapitola 4 představuje výsledky simulací různých verzí Shorova algoritmu. V kapitole 5 pojednejte o dosažení cílů disertační práce, shrňte výsledky výzkumu a nastíňte budoucí směry výzkumu.

碩士
國立交通大學
應用化學系碩博士班
108
Reactions between chlorine atoms and unsaturated hydrocarbons play important roles in atmosphere chemistry. In the marine boundary layer and polluted coastal areas, chlorine atom reactions with alkenes produce alkyl or alkenyl radicals, which may further react with O_2 and become potential contributors to secondary organic aerosols. In the reaction, HCl is produced from either direct abstraction of an allylic hydrogen atom by the chlorine atom or addition-elimination, in which the chlorine atom first adds to the C=C double bond to form a chloroalkyl radical, followed by abstraction of an hydrogen atom of the methyl moiety to produce HCl and an alkenyl radical. Stabilized chloro-alkenyl radicals are produced from the addition reaction at high pressure. The relative importance of the addition reaction and hydrogen atom abstraction reaction depends on the environmental pressure and temperature. Recently, a roaming mechanism mediating the addition-elimination pathway in the reaction of Cl + isobutene was suggested; it becomes significant at low collision energies. This roaming mechanism was further supported through observation of the enhanced rate for the formation of HCl, which is probed with a step-scan FTIR emission spectroscopy, when sufficient Ar was added in the system to enhance the roaming behavior. The added argon quenches efficiently the kinetic energy of photo-induced chlorine atom to reduce the collision energy. This study is aimed at investigating the HCl formation pathways in the reaction of Cl + trans-2-butene with a step-scan time-resolved FTIR spectrometer. The reaction of Cl + trans-2-butene was carried out at 298 K under pseudo-first-order condition, in which argon (or helium) buffer gas in varied proportion was added to the system so that the total pressure reached 0.48, 1, 2, and 3 Torr, respectively. IR emission signal of HCl in the region of 2400-3300 cm^(-1) was observed. Emission lines of HCl(v=1, J≤11) and HCl(v=2, J≤7) were observed with mean rotational energy of ~3 kJ mol^(-1) and [HCl(v=2)]⁄[HCl(v=1)] =0.10±0.01. We performed the kinetic simulation on temporal profiles of HCl with the MATLAB program according to the proposed mechanism. Literature rate coefficients, kabs=4.6×10^(-11) cm^(3) molecule^(-1) s^(-1), kfor=2.98×10^(-10) cm^(3) molecule^(-1) s^(-1), and kM'(0)=4×10^(-28)-10×10^(-28) cm^(3) molecule^(-1) s^(-1) were fixed during the simulation; ke, krev, kq, ϕ2/ϕ1, and ε2/ε1 were fitted with the temporal profiles. In the reaction of Cl + trans-2-butene, as the total pressure increases, the derived kae decreases, and kadd enhances. At total pressure of 0.48 Torr in which Ar was added as the quenching gas, ke/kfor [alkene] and kae/kfor are greater than those in the He environment; these results implying that under conditions with lower collision energies, the contribution of the addition-elimination to the formation of HCl increases. This observation is consistent with the characteristics of the roaming mechanism proposed by Joalland et al. and Estillore et al., who indicated that roaming mechanism might play an important role in the reaction of Cl + trans-2-butene at small collision energy.