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Principles of NMR
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Nuclear magnetic resonance spectroscopy (NMR) was first developed in 1946 by research groups at Stanford and M.I.T., in the USA. The radar technology developed during World War II made many of the electronic aspects of the NMR spectrometer possible. With the newly developed hardware physicists and chemists began to apply the technology to chemistry and physics problems. Over the next 50 years NMR developed into the premier organic spectroscopy available to chemists to determine the detailed chemical structure of the chemicals they were synthesizing. Another well-known product of NMR technology has been the Magnetic Resonance Imager (MRI), which is utilized extensively in the medical radiology field to obtain image slices of soft tissues in the human body. In recent years, NMR has moved out of the research laboratory and into the on-line process analyzer market. This has been made possible by the production of stable permanent magnet technologies that allow high-resolution 1 H NMR spectra to be obtained in a process environment. The NMR phenomenon is based on the fact that nuclei of atoms have magnetic properties that can be utilized to yield chemical information. Quantum mechanically subatomic particles (protons, neutrons and electrons) have spin. In some atoms (eg 12 C, 16 O, 32 S) these spins are paired and cancel each other out so that the nucleus of the atom has no overall spin. However, in many atoms (1 H, 13 C, 31 P, 15 N, 19 F etc) the nucleus does possess an overall spin. To determine the spin of a given nucleus one can use the following rules: If the number of neutrons and the number of protons are both even, the nucleus has no spin. If the number of neutrons plus the number of protons is odd, then the nucleus has a half-integer spin (i.e. 1/2, 3/2, 5/2). If the number of neutrons and the number of protons are both odd, then the nucleus has an integer spin (i.e. 1, 2, 3).
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... There are many excellent monographs on NMR [31,32,33]. There are also many other nice internet website resources offering concise but highly useful information about NMR; e.g., [34,35,36]. Let us briefly explain the physics of NMR by following ...
... Edwards [34]. The NMR phenomenon is based on the fact that the spin of nuclei of atoms have magnetic properties that can be utilized to yield chemical, physical, and biological information. ...
This dissertation focuses on two connected areas: quantum computation and quantum control. Two proposals to construct a quantum computer, using nuclear magnetic resonance (NMR) and superconductivity, are introduced. We give details about the modeling, qubit realization, one and two qubit gates and measurement in the language that mathematicians can understand and fill gaps in the original literatures. Two experimental examples using liquid NMR are also presented. Then we proceed to investigate an example of quantum control, that of a magnetometer using quantum feedback. Previous research has shown that feedback makes the measurement robust to an unknown parameter, the number of atoms involved, with the assumption that the feedback is noise free. To evaluate the effect of the feedback noise, we extend the original model by an input noise term. We then compute the steady state performance of the Kalman filter for both the closed-loop and open-loop cases and retrieve the estimation error variances. The results are compared and criteria for evaluating the effects of input noise are obtained. Computations and simulations show that the level of input noise affects the measurement by changing the region where closed loop feedback is beneficial.
... ppm, corresponding to the aromatic protons of the naphthyl ring and amide group (−(CO)NH), respectively. 60 A highly intense and sharp resonance signal at δ H 4.80 ppm was obtained from the solvent (D 2 O) used for the analysis. The hydroxyl proton (C−OH) present in the graphene moiety exhibits a characteristic medium resonance peak at δ H 3.43 ppm. ...
Selective and sensitive detection of highly toxic chemicals by a suitable, fast, inexpensive and trustworthy method is vital due to its serious health threats to humankind and breach of public security caused by unexpected terrorist attacks and industrial accidents. Phosgene or Carbonyl dichloride is widely employed in many chemical industries, pharmaceuticals and in pesticide production, which is extremely toxic by severe (short-term) inhalation exposure. Because of the non-existing of phosgene sensor in aqueous solution and the immense emphasis gained by nanomaterials, especially carboneous materials, augmented attention has been given to the development of a fluorophore functionalized carbon-based method to detect this noxious substance. In this study, surfactant free 1,8-diaminonaphthalene (DAN) functionalized graphene quantum dots (DAN–GQDs) were prepared to detect phosgene in aqueous solution. The FE-SEM and HR-TEM analyses confirm the as-prepared DAN–GQDs morphology as nanobuds (NBs) with average diameter of ca. 35-40 nm. The crystalline nature, elemental composition and chemical state of DAN–GQDs were analyzed by standard physiochemical techniques. Edge-termination at carboxyl functional group of GQDs with DAN was examined by XPS, Raman, FT-IR and 1H-NMR spectroscopy analyzes. Aqueous solution of DAN–GQDs (4.89×10–9 M) exhibits a strong emission peak at 423 nm upon excitation at 328 nm. Addition of phosgene molecule (0→88 µL) quenches the initial fluorescence intensity of DAN–GQDs (ФF 53.6 → 34.6%) through the formation of stable six-membered cyclized product. The DAN–GQDs displayed excellent selectivity and sensitivity for phosgene (Ka=3.84×102 M-1 and limit of detection (LoD) = 2.26 ppb) over other competing toxic pollutants in water. The time-resolved fluorescence analysis confirms that quenching of DAN–GQDs follows non-radiative relaxation of excited electrons. Furthermore, bioimaging experiments of phosgene in living human breast cancer (HeLa) cells and cell viability test successfully demonstrated the practicability of DAN–GQDs.
... Previous research demonstrated that a systematic addition of an adulterant, with all other variables held constant, produces a linear response in the Q residuals. 22 This is demonstrated for all of the adulterants for classes 1 and 3 in Figure 8A, where the logs of the Q residuals have been plotted as a function of the logs of the adulterant concentrations for the unbinned high-resolution 1 H NMR spectra. The 95% confidence limits are the same as those in Figure 7 and are based on the samples analyzed in phase 1. ...
1H-NMR spectra for 66 commercial powdered milk samples were analyzed by PCA, SIMCA, and pooled, crossed ANOVA. It was found that the sample type (skim milk powder or non-fat dry milk), the supplier, the production site, the processing temperature (high, medium, or low temperature), and the day of analysis provided statistically significant sources of variation. Interestingly, inexact alignment (deviations of ±0.002 ppm) of the spectral reference peak was a significant source of variation and fine alignment was necessary before the variation arising from the other experimental factors could be accurately evaluated. Using non-targeted analysis, the lowest detectable adulteration for dicyandiamide, melamine, and sucrose was 0.05%, maltodextrin and urea was 0.5%, ammonium sulfate and whey was 5%, and soy protein isolate was undetectable using methods described herein. The measurement of variance and detection of adulteration were relatively unaffected by the resolution. Similar results were obtained with un-binned data (0.0003 ppm resolution) and binning of 333 data points (0.1 ppm resolution).
Cryptophanes are a family of molecular containers, characterized by their lipophilic internal cavity. The ability of cryptophanes to encapsulate hyperpolarized xenon has opened a great opportunity to develop highly sensitive 129-Xe-based MRI molecular tracers. A large number of 129-Xe-cryptophane biosensors have been developed for targeting various biological events. Although this concept is catchy, many challenges have been encountered, specifically in the elaboration of water soluble and easy functionalizable cryptophane derivatives. The work presented in this thesis aims at developing a new straightforward approach to synthesize water soluble cryptophane sensors. These cages are based on cryptophane-[223] derivatives that bear a central carboxylic acid function to selectively graft a sensing unit, and six water soluble precursors on the cryptophanes’ rims. Using these platforms, three different water soluble sensors have been elaborated. These sensors have been characterized by 129Xe NMR spectroscopy to assess their binding properties and responsiveness. An additional aspect of these derivatives is their ability to undergo a solvent-dependent “self-encapsulation” phenomenon. This is characterized by the inclusion of the central functionality grafted on the propelendioxy linker towards the inner cavity of cryptophanes. This phenomenon has been clearly proved by 1H NMR and IR spectroscopy. The effect on the overall chiroptical properties was also investigated by polarimetry, VCD and ECD spectroscopy.
The energy crisis and energy prices are the most important topics nowadays. Since the important source of energy is the petroleum oil; which is close to depletion, so scientists and engineers are striving to discover an alternative source of energy to replace it. Such new source of energy must be renewable to avoid the past shortcomings. One of these sources is what so called bio-fuels which can be derived from particular seeds oil. However, the chosen plants must have the important characteristics of the suitability of growth in our country, low water requirements in agriculture, reduced amount of needed fertilizers, high productivity, longevity and economy of production. This thesis describes the different kinds of alternative fuels, and its advantages and disadvantage of different kinds of vegetable oils available and how to synthesize and treat a volatile fuel from it in order to use in conventional spark-ignition engines. The main aim of this research project is to study the detonation, pre-ignition phenomenon, performance and emissions of this new alternative jojoba bio-gasoline fuel using Recardo E6 variable compression ratio as spark ignition engine that is fueled by different blends of jojoba bio-gasoline with gasoline octane 90. The results show the effect of equivalence ratio, speed, ignition timing, compression ratio, inlet temperature on detonation, and pre-ignition. Also the effect of using different blends of that novel fuel with gasoline on engine performance and emissions. Also, the result data were correlated to give the designer an access to the tool he needs for developing an existing engine or in the design of a new engine.
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