Monofluorinated analogues of polybrominated diphenyl ethers as analytical standards: synthesis, NMR, and GC-MS characterization and molecular orbital studies

Polybrominated diphenyl ethers (PBDEs), a group of 209 individual congeners distinguishable by the number and position of bromines, are produced for use as flame retardants in consumer goods. PBDEs have become ubiquitous environmental contaminants, present in increasing levels in the environment and humans. In the present study, 10 individual monofluorinated analogues of PBDEs (F-PBDEs) and one difluorinated PBDE (FF-PBDE) were synthesized and characterized, and their gas chromatographic (GC) and mass spectrometric (MS) characteristics determined. The synthesis method utilized a nucleophilic reaction of bromophenols with diphenyliodonium salts and the perbromination of fluorosubstituted diphenyl ethers. Reaction yields were between 10% and 59% with > or = 98% purity. Apart from the aromatic ring carrying the fluorine atom, only minor chemical nuclear magnetic resonance (NMR) shift changes were observed in comparison to the corresponding parent PBDEs, with the exception that the J(F,H) coupling was stronger. Our preliminary data show that F-PBDEs and PBDEs have comparable retention times in gas chromatography with F-PBDEs demonstrating in general shorter or identical retention times, depending on the pattern of fluorine substitution. We also calculated the torsion angles and the dipole moments for both and report that there is a good correlation between GC retention times and the torsion angles but not with dipole moments. In MS, the difference of the ion peaks of the F-PBDE/ PBDE pairs is m/z 19 (F), which allows a simultaneous MS detection without separation. On the basis of GC separation, simultaneous MS detection, and the stability of fluorine due to its generally resistance to nucleophilic displacement, we propose that F-PBDEs may function as valuable potential standards, markers, and tracers in environmental analysis.     

Flood Frequency Analysis of Interconnected Rivers by Copulas

Flood frequency analysis (FFA) considering the confluence of interconnected rivers is important for hydraulic structures (such as dams or diversions) design, but it has received little attention. This study develops a copula-based method for FFA and quantile estimation considering the confluence of two interconnected rivers, along with the uncertainty estimation by a nonparametric bootstrapping algorithm. Flood probability distribution and return periods are estimated for the two rivers by mapping from bivariate to univariate peak flow quantile estimation. The methodology is applied to the case study of Qezel Ozan and Shahrud Rivers which merge to one of the largest reservoir dams in Iran: Sefidrud (Manjil) dam. According to the results from Peak flow records from Gilvan station (GPF) at Qezel Ozan River and from Loshan station (LCF) at Shahrud River, Gaussian copula with Weibull and gamma margins fits best. Also, it shows that some peak flow quantiles with the same magnitudes have a different probability of occurrences at the confluence of the rivers, and the bivariate estimation uncertainty usually plays an important role in FFA. These findings suggest the use of bivariate instead of univariate distributions to the peak flows at the confluence of interconnected rivers, in which the sampling uncertainty should be considered.

     

Performance of an ultra-compact biofilm reactor treating domestic and synthetic wastewaters

The performance of an ultra-compact biofilm reactor (UCBR) treating domestic wastewater (DWW) collected from a local water reclamation plant; and gradually shifting to a mono-type carbon source synthetic wastewater (SWW) combined with DDW (CWW) and finally SWW; was investigated in this study. The total COD concentrations of influent DWW and CWW/SWW were 413.6 ± 80.8 mg/L and 454.9 ± 51.3 mg/L, respectively. The UCBR was able to achieve average total COD removal efficiencies of 70 ± 10% and 80 ± 4% for DWW and SWW respectively. The total COD concentrations of the effluent of DWW and CWW/SWW were 122.5 ± 44.4 mg/L and 89.7 ± 10.3 mg/L, respectively. These observations suggested that heterotrophs in the UCBR system were able to better assimilate and remove carbon of mono-type SWW compared to diverse carbon sources such as DWW; although the influent soluble COD concentrations of the SWW were higher than those of the DWW. However, the effluent NH(4)(+)-N concentrations for both types of wastewater were rather similar, <3.0 mg/L; although the influent NH(4)(+)-N concentrations of the DWW were 1.5 times those of the SWW.     

Fingerprint reference point detection for image retrieval based on symmetry and variation

Reference point plays an important role in fingerprint identification systems. The reference point is widely used for the fingerprint retrieval in large-scale databases. This paper proposes a novel algorithm for detecting a convex core point as a unique reference point consistently and accurately for all types of fingerprints. In order to detect robust core point candidates, a modified complex filter, called semi-radial symmetry filter, is proposed to detect correctly rotational symmetries of core points. Moreover, a vertical orientation variation feature, called VORIV feature, is proposed to remove spurious core points and concave core points. Therefore, the proposed technique computes the Variation and Symmetry Combined Energy (VSCOME). Then, the reference point is located by searching the global VSCOME maximum. The experimental results on the public database (FVC2004 DB1 set A) show that the proposed technique exhibits a very high robustness and gets the best performance in comparing with other approaches in literature.     

Comparison of two hyperspectral imaging and two laser-induced fluorescence instruments for the detection of zinc stress and chlorophyll concentration in bahia grass (Paspalum notatum Flugge.)

Bahia grass (Paspalum notatum Flugge.) plants were grown in silica sand and irrigated daily with one of five levels of Zn (0, 0.5, 25, 50, or 100 mg l⁻¹) to determine the effects of the heavy metal on the growth and development of plant canopies. Healthy and stressed plants were measured with two hyperspectral imagers, laser-induced fluorescence spectroscopy (LIFS), and laser-induced fluorescence imaging (LIFI) systems in order to determine if the four handheld remote sensing instruments were equally capable of detecting plant stress and measuring canopy chlorophyll levels in bahia grass. Symptoms of bahia grass plants grown at deficient (0 mg l⁻¹) or toxic (25, 50, or 100 mg l⁻¹) concentrations of Zn were dominated by leaf chlorosis and plant stunting. Leaf fresh weight, leaf dry weight, CO₂ assimilation, total chlorophyll, and leaf thickness followed (+) quadratic models in which control plants (0.5 mg l⁻¹ Zn) exhibited higher responses than plants grown at either deficient or toxic levels of Zn. Normalized difference vegetation index [NDVI=(NIR−Red)/(NIR+Red)] and ratio vegetation index [RVI=R₇₅₀/R₇₀₀, in which R denotes reflectance] values were calculated for calibrated digital images from both hyperspectral imagers. The NDVI and RVI values from both hyperspectral imagers were fit best by (+) quadratic models when treatments were constrained between 0 and 100 mg l⁻¹ Zn, but were fit best by linear regression models with (−) slopes when treatments were constrained between 0.5 and 100 mg l⁻¹ Zn. Furthermore, both NDVI and RVI algorithms were effective in predicting the concentrations of chlorophyll in canopies of bahia grass grown at the various levels of Zn. In contrast, red/far-red (R/FR) fluorescence ratios estimated from leaf fluorescence values measured with the LIFS and LIFI instruments were fit best by (−) quadratic models when treatments were constrained between 0 and 100 mg l⁻¹ Zn, but were fit best by linear regression models with (+) slopes when treatments were constrained between 0.5 and 100 mg l⁻¹ Zn. A series of regression analyses were conducted among plant biometric, biochemical, and leaf anatomical parameters (treated as independent variables) and the remote sensing algorithms, NDVI, RVI, blue/green (BL/GR), and R/FR (treated as dependant variables). In general, residuals were significantly higher for NDVI and RVI models compared to the BL/GR and R/FR models indicating that the NDVI and RVI algorithms were able to measure total chlorophyll and plant biomass more accurately than the BL/GR and R/FR algorithms. However, unique capabilities of LIFS and LIFI instruments continue to argue for the development of laser-induced fluorescence remote sensing technologies.     

Efficient Large-Scale Filter/Filterbank Design via LMI Characterization of Trigonometric Curves

Many filter and filterbank design problems can be posed as the optimization of linear or convex quadratic objectives over trigonometric semi-infinite constraints. Recent advances in design methodology are based on various linear matrix inequality (LMI) characterizations of the semi-infinite constraints, and semidefinite programming (SDP) solutions. Despite these advances, the design of filters of several hundredth order, which typically arise in multicarrier communication and signal compression, cannot be accommodated. This hurdle is due mainly to the large number of additional variables incurred in the LMI characterizations. This paper proposes a novel LMI characterization of the semi-infinite constraints that involves additional variables of miminal dimensions. Consequently, the design of high-order filters required in practical applications can be achieved. Examples of designs of up to 1200-tap filters are presented to verify the viability of the proposed approach.     

Evaluation of the instrumental quality of pressure-assisted thermally processed carrots

ABSTRACT:  This study was conducted to compare the effectiveness of pressure-assisted thermal processing (PATP) in preserving the texture, color, and carotene content of carrot cylinders in the pressure range of 500 to 700 MPa and the temperature range of 95 to 121 °C. The effectiveness of PATP was compared with that of conventional thermal processing (TP) by matching carrot preprocess temperature history. Results indicated that under comparable process temperatures (up to 105 °C), PATP retained the carrot quality attributes such as color and carotene content better than TP. However, process and preprocess thermal history at 121 °C greatly influenced carrot textural change and pressure protective effects were less pronounced. This study demonstrated that PATP has the potential to produce low-acid foods with a relatively better quality than TP.     

Dehydration by Successive Pressure Drops for Drying Paddy Rice Treated by Instant Controlled Pressure Drop

The aim of the present work was to study the application of the dehydration by successive pressure drops (DDS) process to different varieties of paddy rice initially treated by the instantaneous controlled pressure drop (DIC), which is a high-temperature, short time postharvest treatment (moisture content about 20–25% dry basis) and takes less than 30 s. DIC paddy rice is dried by DDS in a relatively short time and a high milling quality is obtained (12–13% db in about 2 h). The final rice is white, easily distinguishing it from the standard parboiled one. Without a tempering period, DDS rice has less than 3% of broken grains, with a high organoleptic quality (preservation of the natural aroma with a firm and non-sticky texture), and the cooking time of both brown (whole) and white DIC rice is very short (15 and 7 min, respectively).     

Correlations, partitioning and bioaccumulation of heavy metals between different compartments of Lake Balaton

Correlations between trace metals in dissolved and particulate phases, zooplankton, mussels and sediments in Lake Balaton were investigated. The degree of correlation between the various metals was different in each of the investigated compartments. Particulate metal concentrations (microg g(-1)) were anti-correlated with suspended particulate matter (SPM) (mg l(-1)), indicating a dilution effect, while total metal concentrations in the water column (microg l(-1)) were highly correlated with SPM, implying a major influence of the turbidity on the total metal concentrations. Between compartments, not many significant correlations were recognized. Only Ba, Ca, Sr and Mg are correlated in the sediments and in the particulate phase, suggesting common sources for both compartments. Partitioning coefficients (Kd) of trace metals between dissolved and particulate phases are generally low, typical for natural water and fairly stable over the lake. Most of the trace metals (Zn, Co, Cd and Pb) exist in the particulate phase (for about 70% of the total metal load). Cu and Ni are exceptions, showing a more equal distribution. Bioconcentration factors (BCF) of zooplankton and mussels were comparable to those of other natural waters. A negative biomagnification from suspended particulate matter to zooplankton and from sediment to mussel was recognized for all trace metals, except a small enrichment of Zn in zooplankton and Cd in mussel. Four factors were recognized in SPM and in sediments but they did not contain the same group of metals. Cluster analysis showed that metal accumulations in the sediments were different between northern and southern shores and in SPM between western and eastern areas.     

Size-dependent nonlocal strain gradient modeling of hexagonal beryllium crystal nanoplates

International Journal of Mechanics and Materials in Design - In this paper, a size dependent numerical model for free vibration and bending analyses of hexagonal beryllium crystal (HBC) nanoplates...