Flammability studies are conducted to evaluate the behavior of materials exposed to fire. In this study, microscale combustion calorimetry (MCC) and cone calorimetry methods were applied to acquire the flammability characteristics of red and grey extruded polystyrene (XPS) samples. To understand the effect of changes between parameters, Pearson’s correlation coefficient was used to examine their linear relationships. From the research, moderate and weak correlations were recorded between the total heat release rates from both methods for red and grey XPS, respectively. Plotting peak heat release rate against heat release temperature for MCC and ignition temperature for cone test showed that 25, 35 and 50 kW m?2 incident heat fluxes of the cone test fall within 0.2 K s?1 and 0.5 K s?1 heating rates of MCC. Also, all the MCC parameters except char yield and total heat release presented good correlations with the cone calorimetry flammability characteristics. Hence, MCC could be used in conjunction with cone calorimetry to accurately and reliably assess the flammability of materials.
ABSTRACTWe report the unexpected observation of columnar mesophase formation in a simple 2,7-dibromotetramethoxytriphenylene – by far the most lightly substituted discotic mesogen in this class. This derivative was prepared alongside the 3,6-dibromotriphenylene isomer to demonstrate an alternative, modified synthetic strategy that permits late-stage interchange of alkyl chain substituents. The new method is employed alongside the original route to deliver several new materials, including a conjugated ferrocene–triphenylene–ferrocene triad, a BODIPY–triphenylene–BODIPY triad and a new nematic twin linked through imine bridges. 相似文献
In addition to matrix effects, common interferences observed in liquid chromatography/tandem mass spectrometry (LC/MS/MS) analyses can be caused by the response of drug-related metabolites to the multiple reaction monitoring (MRM) channel of a given drug, as a result of in-source reactions or decomposition of either phase I or II metabolites. However, it has been largely ignored that, for some drugs, metabolism can lead to the formation of isobaric or isomeric metabolites that exhibit the same MRM transitions as parent drugs. The present study describes two examples demonstrating that interference caused by isobaric or isomeric metabolites is a practical issue in analyzing biological samples by LC/MS/MS. In the first case, two sequential metabolic reactions, demethylation followed by oxidation of a primary alcohol moiety to a carboxylic acid, produced an isobaric metabolite that exhibits a MRM transition identical to the parent drug. Because the drug compound was rapidly metabolized in rats and completely disappeared in plasma samples, the isobaric metabolite appeared as a single peak in the total ion current (TIC) trace and could easily be quantified as the drug since it was eluted at a retention time very close to that of the drug in a 12-min LC run. In the second example, metabolism via the ring-opening of a substituted isoxazole moiety led to the formation of an isomeric product that showed an almost identical collision-induced dissociation (CID) MS spectrum as the original drug. Because two components were co-eluted, the isomeric product could be mistakenly quantified and reported by data processing software as the parent drug if the TIC trace was not carefully inspected. Nowadays, all LC/MS data are processed by computer software in a highly automated fashion, and some analysts may spend much less time to visually examine raw TIC traces than they used to do. Two examples described in this article remind us that quality data require both adequate chromatographic separations and close examination of raw data in LC/MS/MS analyses of drugs in biological matrix. 相似文献
The first organometallic BOPHY (BOPHY=bis(difluoroboron)‐1,2‐bis{(pyrrol‐2‐yl)methylene}hydrazine) containing two ferrocene substituents was prepared through a Knoevenagel condensation between tetramethyl substituted BOPHY and ferrocene carboxaldehyde. An unprecedentedly strong long‐range (≈17.2 Å) metal–metal coupling in this new complex was investigated using electrochemical, spectroelectrochemical, and chemical oxidation methods. Electrochemical data is indicative of a 200 mV separation between the first and the second ferrocene‐centered oxidation processes. Formation of the mixed‐valence states and appearance and disappearance of two NIR bands were observed during stepwise oxidation of the first organometallic BOPHY. The electronic structure and the nature of the excited states in this new chromophore were studied by DFT and TDDFT calculations. 相似文献
One recommendation of the national reform movements in mathematics and science is to change the way students are assessed. In this article five formats of alternative assessment forms are described, and suggestions are given on how these methods can be implemented within science and mathematics classrooms. Benefits of each type of assessment are discussed and potential pitfalls are elucidated. Samples of the five formats, journal writing, open-ended problems, portfolios, interviews and performance assessments, are included. 相似文献
An efficient synthesis of biaryl building blocks with multiple point diversities via a Suzuki cross-coupling reaction using a commercially available preformed Pd catalyst 1 was reported. Substituted biaryl anilines and phenols were obtained in one step from commercially available aryl halides. 相似文献
In this paper we demonstrate that the scattering tensors for one phonon Brillouin scattering and for “morphic-induced” Raman scattering can be simply related to known Clebsch-Gordan coefficients. Tensors for crystals with point group symmetry Td and C6v are given. Tensors for higher order processes can be found similarly. 相似文献