The Underlying Chemistry to the Formation of PO2 Radicals from Organophosphorus Compounds: A Missing Puzzle Piece in Flame Chemistry

Reactive species, such as ^.PO₂ and HOPO, are considered of upmost importance in flame inhibition and catalytic combustion processes of fuels. However, the underlying chemistry of their formation remains speculative due to the unavailability of suitable analytical techniques that can be used to identify the transient species which lead to their formation. This study elucidates the reaction mechanisms of the formation of phosphoryl species from dimethyl methyl phosphonate (DMMP) and dimethyl methyl phosphoramidate (DMPR) under well-defined oxidative conditions. Photoelectron photoion coincidence techniques that utilized vacuum ultraviolet synchrotron radiation were applied to isomer-selectively detect the elusive key intermediates and stable products. With the help of in situ recorded spectral fingerprints, different transient species, such as PO₂ and triplet O radicals, have been exclusively identified from their isomeric components, which has helped to piece together the formation mechanisms of phosphoryl species under various conditions. It was found that ^.PO₂ formation required oxidative conditions above 1070 K. The combined presence of O₂ and H₂ led to significant changes in the decomposition chemistry of both model phosphorus compounds, leading to the formation of ^.PO₂. The reaction ^.PO+O₂→^.PO₂+O: was identified as the key step in the formation of ^.PO₂. Interestingly, the presence of O₂ in DMPR thermolysis suppresses the formation of PN-containing species. In a previous study, PN species were identified as the major species formed during the pyrolysis of DMPR. Thus, the findings of this study has shed light onto the decomposition pathways of organophosphorus compounds, which are beneficial for their fuel additive and fire suppressant applications.     

Evaluation of steviol and its glycosides in Stevia rebaudiana leaves and commercial sweetener by ultra-high-performance liquid chromatography-mass spectrometry

Stevia rebaudiana leaves contain non-cariogenic and non-caloric sweeteners (steviol-glycosides) whose consumption could exert beneficial effects on human health. Steviol-glycosides are considered safe; nonetheless, studies on animals highlighted adverse effects attributed to the aglycone steviol. The aim of the present study was to develop and validate two different ultra-high-performance liquid chromatography methods with electrospray ionization mass spectrometry (UHPLC-MS) to evaluate steviol-glycosides or steviol in Stevia leaves and commercial sweetener (Truvia^®). Steviol-glycosides identity was preliminarily established by UV spectra comparison, molecular ion and product ions evaluation, while routine analyses were carried out in single ion reaction (SIR) monitoring their negative chloride adducts. Samples were sequentially extracted by methanol, cleaned-up by SPE cartridge and the analytes separated by UHPLC HSS C₁₈ column (150 mm × 2.1 mm I.D., 1.8 μm). The use of CH₂Cl₂ added to the mobile phase as source of Cl⁻ enhance sensitivity. The LLOD for stevioside, rebaudioside A, steviolbioside and steviol was 15, 50, 10 and 1 ng ml⁻¹, respectively. Assay validation demonstrated good performances in terms of accuracy (89–103%), precision (<4.3%), repeatability (<5.7%) and linearity (40–180 mg/g). Stevioside (5.8 ± 1.3%), rebaudioside A (1.8 ± 1.2%) and rebaudioside C (1.3 ± 1.4%) were the most abundant steviol-glycosides found in samples of Stevia (n = 10) from southern Italy. Rebaudioside A was the main steviol-glycosides found in Truvia^® (0.84 ± 0.03%). The amounts of steviol-glycosides obtained by the UHPLC-MS method matched those given by the traditional LC-NH₂-UV method. Steviol was found in all the leaves extract (2.7–13.2 mg kg⁻¹) but was not detected in Truvia^® (<1 μg kg⁻¹). The proposed UHPLC-MS methods can be applied for the routine quality control of Stevia leaves and their commercial preparations.     

Evidence for heavy hyperhydrogen (Λ)(6)h

Evidence for the neutron-rich hypernucleus (Λ)(6)H is presented from the FINUDA experiment at DAΦNE, Frascati, studying (π+,π-) pairs in coincidence from the K(stop)(-) + (6)Li →(Λ)(6)H + π+ production reaction followed by (Λ)(6)H → (6)He + π- weak decay. The production rate of (Λ)(6) undergoing this two-body π- decay is determined to be (2.9 ± 2.0) × 10(-6)/K(stop)(-). Its binding energy, evaluated jointly from production and decay, is BΛ((Λ)(6)H) = (4.0 ± 1.1) MeV with respect to (5)H+Λ. A systematic difference of (0.98 ± 0.74) MeV between BΛ values derived separately from decay and from production is tentatively assigned to the (Λ)(6)H 0(g.s.)(+) → 1+ excitation.     

A bonding study of c-C5H8 adsorption on Pt(1 1 1)

The chemisorption of cyclopentane (c-C₅H₈) on Pt(1 1 1) has been studied using a qualitative band-structure calculations in the framework of tight-binding implementation with the YAeHMOP package. We modeled the metal surface by a two-dimensional slab of finite thickness with an overlayer of c-C₅H₈, in a (3 × 3) di-σ geometry. The c-C₅H₈ molecule is attached to the surface with its CC atoms bonded mainly with two Pt atoms while the opposite CH₂ bends towards the surface. The PtPt bonds in the underlying surface and the CC bonds of c-C₅H₈ are weakened upon the chemisorption. A noticeable Pt-H and Pt-C interactions has been observed. We found that of Pt band plays an important role in the bonding between c-C₅H₈ and the surface, as do the Pt 6s and 6p_z bands. The HOMO-LUMO bands of c-C₅H₈ are very dispersed, indicative of a strong interaction with the metal surface.     

Fast nosologic imaging of the brain

Magnetic resonance spectroscopic imaging (MRSI) provides information about the spatial metabolic heterogeneity of an organ in the human body. In this way, MRSI can be used to detect tissue regions with abnormal metabolism, e.g. tumor tissue. The main drawback of MRSI in clinical practice is that the analysis of the data requires a lot of expertise from the radiologists. In this article, we present an automatic method that assigns each voxel of a spectroscopic image of the brain to a histopathological class. The method is based on Canonical Correlation Analysis (CCA), which has recently been shown to be a robust technique for tissue typing. In CCA, the spectral as well as the spatial information about the voxel is used to assign it to a class. This has advantages over other methods that only use spectral information since histopathological classes are normally covering neighbouring voxels. In this paper, a new CCA-based method is introduced in which MRSI and MR imaging information is integrated. The performance of tissue typing is compared for CCA applied to the whole MR spectra and to sets of features obtained from the spectra. Tests on simulated and in vivo MRSI data show that the new method is very accurate in terms of classification and segmentation. The results also show the advantage of combining spectroscopic and imaging data.     

Evaluation of allergens in propolis by ultra-performance liquid chromatography/tandem mass spectrometry

The purified extract of propolis is used as a traditional remedy for the treatment of several diseases. Its beneficial activities are mainly attributed to the polyphenolic fraction. Nevertheless, propolis can cause allergic dermatitis and the sensitization rate in humans is increasing significantly mainly in younger subjects. The aim of this study was to develop and validate a selective and sensitive ultra‐performance liquid chromatography tandem mass spectrometry analysis (UPLC/MS/MS) for the evaluation of the amount of caffeic acid and its esters with allergenic action in raw propolis samples and commercial formulations. The separation was carried out on a 1.7 μm C₁₈ BEH Shield column and the detection performed by means of electrospray ionization in negative ion mode with multiple reaction monitoring. The confirmation of formulae of the precursor and product ions was accomplished by injection into a high‐resolution system (FTICR‐MS) using accurate mass measurements. The error was below 1.4 ppm.The range of the standard curves was 0.5–10 μg/mL and dihydrocaffeic acid was used as internal standard (IS). The lower limit of detection (LLOD) for 3‐methyl‐2‐butenyl‐ (3M2B), 3‐methyl‐3‐butenyl‐ (3M3B), 2‐methyl‐2‐butenyl‐ (2M2B), benzyl‐ (CABE), phenylethylcaffeic acid (CAPE) and for caffeic acid (CA) and the IS was 0.1 and 0.3 μg/mL, respectively. The recoveries were in the range 96–104% and the intra‐ and inter‐day precisions were within 6.2%. In the European (n = 8) and Asiatic (n = 3) propolis the most abundant allergens were CABE>3M2B>CAPE>3M3B>CA>2M2B. These compounds were not found in the red (n = 1) and green (n = 1) Brazilian propolis. Hydroalcoholic extracts (n = 6) and tablets (n = 6) were analyzed by the proposed UPLC/MS/MS method. The results showed that in the commercial products CABE, 3M2B, CAPE and 3M3B were also the most abundant. Copyright © 2011 John Wiley & Sons, Ltd.     

Hybrid heuristics for a short sea inventory routing problem

We consider a short sea fuel oil distribution problem where an oil company is responsible for the routing and scheduling of ships between ports such that the demand for various fuel oil products is satisfied during the planning horizon. The inventory management has to be considered at the demand side only, and the consumption rates are given and assumed to be constant within the planning horizon. The objective is to determine distribution policies that minimize the routing and operating costs, while the inventory levels are maintained within their limits. We propose an arc-load flow formulation for the problem which is tightened with valid inequalities. In order to obtain good feasible solutions for planning horizons of several months, we compare different hybridization strategies. Computational results are reported for real small-size instances.     

Corrosion and erosion monitoring in plates and pipes using constant group velocity Lamb wave inspection

Recent improvements in tomographic reconstruction techniques generated a renewed interest in short-range ultrasonic guided wave inspection for real-time monitoring of internal corrosion and erosion in pipes and other plate-like structures. Emerging evidence suggests that in most cases the fundamental asymmetric A₀ mode holds a distinct advantage over the earlier market leader fundamental symmetric S₀ mode. Most existing A₀ mode inspections operate at relatively low inspection frequencies where the mode is highly dispersive therefore very sensitive to variations in wall thickness. This paper examines the potential advantages of increasing the inspection frequency to the so-called constant group velocity (CGV) point where the group velocity remains essentially constant over a wide range of wall thickness variation, but the phase velocity is still dispersive enough to allow accurate wall thickness assessment from phase angle measurements. This paper shows that in the CGV region the crucial issue of temperature correction becomes especially simple, which is particularly beneficial when higher-order helical modes are also exploited for tomography. One disadvantage of working at such relatively high inspection frequency is that, as the slower A₀ mode becomes faster and less dispersive, the competing faster S₀ mode becomes slower and more dispersive. At higher inspection frequencies these modes cannot be separated any longer based on their vibration polarization only, which is mostly tangential for the S₀ mode while mostly normal for the A₀ at low frequencies, as the two modes become more similar as the frequency increases. Therefore, we propose a novel method for suppressing the unwanted S₀ mode based on the Poisson effect of the material by optimizing the angle of inclination of the equivalent transduction force of the Electromagnetic Acoustic Transducers (EMATs) used for generation and detection purposes.     

Assessment of early response to concurrent chemoradiotherapy in cervical cancer: value of diffusion-weighted and dynamic contrast-enhanced MR imaging

Purpose

To investigate diffusion-weighted (DWI) and dynamic contrast-enhanced MR imaging (DCE-MRI) as early response predictors in cervical cancer patients who received concurrent chemoradiotherapy (CCRT).

Materials and methods

Sixteen patients with cervical cancer underwent DWI and DCE-MRI before CCRT (preTx), at 1 week (postT1) and 4 weeks (postT2) after initiating treatment, and 1 month after the end of treatment (postT3). At each point, apparent diffusion coefficient (ADC) and DCE-MRI parameters were measured in tumors and gluteus muscles (GM). Tumor response was correlated with imaging parameters or changes in imaging parameters at each point.

Results

At each point, ADC, K^trans and V_e in tumors showed significant changes (P < 0.05), as compared with those of GM (P > 0.05). PostT1 tumor ADCs showed a significant correlation with tumor size response at postT2 (P = 0.041), and changes in tumor ADCs at postT1 had a significant correlation with tumor size (P = 0.04) and volume response (P = 0.003) at postT2. In tumors, preTx K^trans and V_e showed significant correlations with tumor size at postT3 (P = 0.011) and tumor size response at postT2 (P = 0.019), respectively.

Conclusion

DWI and DCE-MRI, as early biomarkers, have the potential to evaluate therapeutic responses to CCRT in cervical cancers.