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71.
Hematite with different particle sizes was obtained through isothermal annealing and mechanochemical ball-milling methods.
The hematite phase is very stable under air atmosphere. The thermal stabilities of hematite under argon atmosphere were characterized
by thermal analysis studies up to 800 °C using a simultaneous DSC–TG technique. The lattice parameters a and c of hematite with different particle sizes were extracted from the Rietveld structural refinement of powder X-ray diffraction
patterns. Decomposition of hematite into a lower oxidation state in inert argon atmosphere was studied by the TG experiments
for the first time and the enthalpy associated with the decomposition reaction was determined from the DSC studies. Particle
size has a strong effect on the thermal behavior of hematite samples. Ball-milled hematite samples with smaller particle size
showed that the phase transformation was extended to higher temperature range with larger enthalpy. Hematite with larger average
particle size showed higher stability under argon atmosphere. 相似文献
72.
Monica Gulmini Marco Pace Gabriella Ivaldi Mariamaddalena Negro Ponzi Piero Mirti 《Journal of Non》2009,355(31-33):1613-1621
This paper discusses the morphological and chemical features of the weathering products on Sasanian glass finds excavated at the ancient Sasanian town of Veh Arda?īr, some 30 km south of Baghdad (Iraq), and dated from the third to the sixth century. All the considered fragments represent soda-lime glass, with MgO contents between 3% and 8%, resulting from the use of soda-rich plant ash as a flux; within this general frame, two productions can be distinguished due to their MgO to K2O ratio. Four main alteration typologies were observed by visual examination of the excavated samples; these were studied by scanning electron microscopy, energy dispersive X-ray analysis, inductively coupled plasma-mass spectrometry, X-ray diffraction and thermal analysis. Different alteration features were generally observed for samples belonging to the two compositional groups. In particular, samples with higher MgO to K2O ratios show definitely thinner crusts, associated with alteration plugs going down into the glass. Moreover, gray or black crusts are related to the presence of manganese at significant levels in the original glass. 相似文献
73.
Monica R. Nemtanu Mirela Brasoveanu Viorica Meltzer Elena Pincu C. Oproiu 《Journal of Thermal Analysis and Calorimetry》2009,97(1):309-313
The purpose of the present work deals with the evaluation of the electron beam irradiation effects on some natural products
based on thermal analysis. Some natural products with therapeutic contributions (artichoke, sea buckthorn, common sage, stonebreaker
and cloves) were irradiated with doses up to 9 kGy using accelerated electron beam. The thermal profiles lead to identify
three phenomena: dehydration — volatilization, irreversible degradation — molecular reorganization and residue decomposition.
The radio-induced degradations determine slight shifts of the temperatures where these phenomena occur. The energetic value
of the studied products is affected by e-beam treatment depending on irradiation dose. 相似文献
74.
Pietro Franceschi Roland Thissen Odile Dutuit Christian Alcaraz Heloise Soldi-Lose Davide Bassi Daniela Ascenzi Paolo Tosi Jan Zabka Zdenek Herman Marcello Coreno Monica de Simone 《International journal of mass spectrometry》2009,280(1-3):119
The long-lived excited states of doubly charged rare gases can markedly affect their reactivity. In this paper we demonstrate the presence of strong state-specific effects in the charge exchange of Ar2+ (3P, 1D and 1S) with several neutral targets (He, Ne, Kr, Xe, D2, and CH4). State sensitive measurements have been performed by producing the different Ar2+ electronic states via tunable synchrotron radiation (Elettra-Trieste, Italy and SuperACO-Orsay, France). From the product ion yield data of charge transfer, state-selected total cross-sections have been deduced. Using the state-specific reactivity of Ar2+ towards different neutral targets, it has been possible to extract the photon-energy-dependent production branching of the three doubly charged states and to investigate the autoionization dynamics of neutral or singly charged Ar in the vicinity of the double ionization threshold. 相似文献
75.
Monica Magureanu Daniela Piroi Florin Gherendi Nicolae Bogdan Mandache Vasile Parvulescu 《Plasma Chemistry and Plasma Processing》2008,28(6):677-688
The decomposition of methylene blue (MB) in aqueous solution was investigated using a pulsed corona discharge. The discharge
was ignited in the gas bubbled in the solution through several needle electrodes. The influence of treatment time, volume
of the treated solution and initial concentration of the dye in solution on MB degradation was studied. The effect of the
nature of the gas introduced was also investigated. For the same energy input, MB conversion increased in the order air < argon < oxygen.
When using oxygen, the decomposition of MB exceeded 95% after ~20 min plasma treatment. Higher efficiency was obtained for
higher treated volume and higher initial concentration. At 90% conversion the yield obtained with oxygen was ~5 g/kWh for
an initial concentration of 150 mg/l and a treated volume of solution of 100 ml. 相似文献
76.
77.
Monica E. Bad Dumitrescu 《Annals of the Institute of Statistical Mathematics》1987,39(1):211-218
Summary The Bayesian estimation problem for the parameter θ of an exponential probability distribution is considered, when it is assumed
that θ has a natural conjugate prior density and a loss-function depending on the squared error is used. It is shown that,
with probability one, the posterior density of the Bayesian—centered and scaled parameter converges pointwise to the normal
probability density. The weak convergence of the posterior distributions to the normal distribution follows directly. Both
correct and incorrect models are studied and the asymptotic normality is stated respectively. 相似文献
78.
Serpe MJ Whitehead JR Rivera M Clark RL Craig SL 《Colloids and surfaces. A, Physicochemical and engineering aspects》2009,346(1-3):20-27
Single-molecule force spectroscopy, as implemented in an atomic force microscope, provides a rarely used method by which to monitor dynamic processes that occur near surfaces. Here, a methodology is presented and characterized that facilitates the study of polymer bridging across nanometer-sized gaps. The model system employed is that of DNA-based reversible polymers, and an automated procedure is introduced that allows the AFM tip–surface contact point to be automatically determined, and the distance d between opposing surfaces to be actively controlled. Using this methodology, the importance of several experimental parameters was systematically studied, e.g. the frequency of repeated tip/surface contacts, the area of the substrate surface sampled by the AFM, and the use of multiple AFM tips and substrates. Experiments revealed the surfaces to be robust throughout pulling experiments, so that multiple touches and pulls could be carried out on a single spot with no measurable affect on the results. Differences in observed bridging probabilities were observed, both on different spots on the same surface and, more dramatically, from one day to another. Data normalization via a reference measurement allows data from multiple days to be directly compared. 相似文献
79.
An eco-friendly tandem tosylation/Ferrier N-glycosylation of amines catalyzed by Er(OTf)3 in 2-MeTHF
Monica Nardi Natividad Herrera Cano Antonio De Nino Maria Luisa Di Gioia Loredana Maiuolo Manuela Oliverio Ana Santiago Diletta Sorrentino Antonio Procopio 《Tetrahedron letters》2017,58(18):1721-1726
Er(OTf)3 in 2-MeTHF provides a new and eco-friendly process for Ferrier glycosylation of sulfonamides and amino acids with various N-nucleophiles.The stereoselective synthesis of 2,3-unsaturated-N-pseudoglycals was carried out with 3,4,6-tri-O-acetyl-d-glucal and different nucleophiles affording good results in a short time. 相似文献
80.
The possibility provided by Chemometrics to extract and combine (fusion) information contained in NIR and MIR spectra in order to discriminate monovarietal extra virgin olive oils according to olive cultivar (Casaliva, Leccino, Frantoio) has been investigated.Linear discriminant analysis (LDA) was applied as a classification technique on these multivariate and non-specific spectral data both separately and jointly (NIR and MIR data together).In order to ensure a more appropriate ratio between the number of objects (samples) and number of variables (absorbance at different wavenumbers), LDA was preceded either by feature selection or variable compression. For feature selection, the SELECT algorithm was used while a wavelet transform was applied for data compression.Correct classification rates obtained by cross-validation varied between 60% and 90% depending on the followed procedure. Most accurate results were obtained using the fused NIR and MIR data, with either feature selection or data compression.Chemometrical strategies applied to fused NIR and MIR spectra represent an effective method for classification of extra virgin olive oils on the basis of the olive cultivar. 相似文献