FISHER'S INFORMATION MATRIX FOR SEASONAL AUTOREGRESSIVE-MOVING AVERAGE MODELS

Abstract. Two procedures are described for obtaining Fisher's information matrix of a multiplicative seasonal autoregressive-moving average process. They can be useful in determining the asymptotic covariance matrix of Gaussian maximum likelihood estimators of the parameters. Components of the information matrix are expressed in the first procedure as integrals of rational functions. The second procedure makes use of the autocorrelation function of several autoregressive processes.     

Lyso platelet activating factor (LysoPAF) and its enantiomer. Total synthesis and carbon-13 NMR spectroscopy

Described is a reaction sequence for the total synthesis of lyso platelet activating factor (lysoPAF; 1-O-alkyl-sn-glycero-3-phosphocholine) and its enantiomer. The procedure is versatile and yields optically pure isomers of defined chain length. The synthesis is equally suited for the preparation of lysoPAF analogues and its enantiomers with unsaturation in the long aliphatic chain. First,rac-1(3)-O-alkylglycerol is prepared by alkylation ofrac-isopropylideneglycerol with alkyl methanesulfonate followed by acid-catalyzed removal of the ketal group. The primary hydroxy group of alkylglycerol is then protected by tritylation, the secondary hydroxy group is acylated, and the protective trityl group is removed under mild acidic conditions with boric acid on silicic acid, essentially without acyl migration. Condensation of the diradylglycerol with bromoethyl dichlorophosphate in diethyl ether, hydrolysis of the resulting chloride, and nucleophilic displacement of the bromine with trimethylamine givesrac-1-O-alkyl-2-acylglycero-3-phosphocholine in good overall yield. The racemic alkylacylglycerophosphocholine is finally treated with snake venom phospholipase A₂ (Ophiophagus hannah) which affords 1-O-alkyl-sn-glycero-3-phosphocholine (lysoPAF) of natural configuration in optically pure form. The “unnatural” 3-O-alkyl-2-O-acyl-sn-glycerol-1-phosphocholine enantiomer, which is not susceptible to phospholipase A₂ cleavage, gives 3-O-alkyl-sn-glycero-1-phosphocholine upon deacylation with methanolic sodium hydroxide. Homogeneity and structure of the intermediates and final products were ascertained by carbon-13 nuclear magnetic resonance spectroscopy on monomeric solutions.     

Impact of the Cd2+ treatment on the electrical properties of Cu2ZnSnSe4 and Cu(In,Ga)Se2 solar cells

The present contribution aims at determining the impact of modifying the properties of the absorber/buffer layer interface on the electrical performance of Cu₂ZnSnSe₄ (CZTSe) thin‐film solar cells, by using a Cd²⁺ partial electrolyte (Cd PE) treatment of the absorber before the buffer layer deposition. In this work, CZTSe/CdS solar cells with and without Cd PE treatment were compared with their respective Cu(In,Ga)Se₂ (CIGSe)/CdS references. The Cd PE treatment was performed in a chemical bath for 7 min at 70 °C using a basic solution of cadmium acetate. X‐ray photoemission spectroscopy measurements have revealed the presence of Cd at the absorber surface after the treatment. The solar cells were characterized using current density–voltage (J–V), external quantum efficiency, and drive‐level capacitance profiling measurements. For the CZTSe‐based devices, the fill factor increased from 57.7% to 64.0% when using the Cd PE treatment, leading to the improvement of the efficiency (η) from 8.3% to 9.0% for the best solar cells. Similar observations were made on the CIGSe solar cell reference. This effect comes from a considerable reduction of the series resistance (R_S) of the dark and light J–V, as determined using the one‐diode model. The crossover effect between dark and light J–V curves is also significantly reduced by Cd PE treatment. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination of the Composition of Commercial Tannin Extracts by Liquid Secondary Ion Mass Spectrometry (LSIMS)

The composition of various commercial tannin extracts were determined by liquid secondary ion mass spectrometry (LSIMS). Spectra were obtained directly from tannin extracts without any pre-separation. Eight different tannin powders were analysed: three gallotannins (Chinese, Turkish, tara), three ellagitannins (sweet chestnut, pendunculata oak, sessile oak), one mixed hydrolysable tannin (myrabolans) and one proanthocyanidin (grape seeds). This method enabled the main molecules in these powders to be identified.     

Biosynthetic Plasticity Enables Production of Fluorinated Aurachins

Enzyme promiscuity has important implications in the field of biocatalysis. In some cases, structural analogues of simple metabolic building blocks can be processed through entire pathways to give natural product derivatives that are not readily accessible by chemical means. In this study, we explored the plasticity of the aurachin biosynthesis pathway with regard to using fluoro- and chloroanthranilic acids, which are not abundant in the bacterial producers of these quinolone antibiotics. The incorporation rates of the tested precursor molecules disclosed a regiopreference for halogen substitution as well as steric limitations of enzymatic substrate tolerance. Three previously undescribed fluorinated aurachin derivatives were produced in preparative amounts by fermentation and structurally characterized. Furthermore, their antibacterial activities were evaluated in comparison to their natural congener aurachin D.     

Transition and flow boiling heat transfer inside a horizontal tube

Experiments on transition and flow boiling heat transfer with refrigerant R114 inside a horizontal tube were performed at bubble flow, critical heat flux and in the transition region between bubble flow and film boiling at mass fluxes between 1200 and 4000 kg/m² s and in the pressure range between 5 and 15 bar. In comparison with pool boiling bubble flow heat transfer depends essentially on the mass flow rates and on the vapor quality. The critical heat flux depends less on the temperature difference than in pool boiling heat transfer and exhibits a maximal and a minimal value as a function of the pressure. The critical heat flux increases with mass flow rate as already shown by Collier. In the region of transition boiling the heat flux over the difference between wall and saturation temperature approaches a horizontal curve. Therefore in this region an evaporator may always be operated under stable conditions and burn out does not occur.     

Synthesis and electrochemical properties of Li[Li0.07Ni0.1Co0.6Mn0.23]O2 as a possible cathode material for lithium-ion batteries

The layered Li[Li_0.07Ni_0.1Co_0.6Mn_0.23]O₂ materials were synthesized by sol-gel method with glycine or citric acid as chelating agent. The prepared materials were characterized by means of XRD, SEM and Raman spectroscopy. Li/Li[Li_0.07Ni_0.1Co_0.6Mn_0.23]O₂ cells were assembled and subjected to charge-discharge studies at different C rates, viz 0.2, 1, 2 and 4 C. Although the samples showed less discharge capacity at 4 C rate the fade in capacity per cycle is lesser than that of capacity fade at 0.2 C rate. The citric acid assisted sample is found to be superior in terms of discharge capacity, capacity retention rate and also in thermal stability to that of sample prepared with glycine as chelating agent.     

Dietary intakes and food sources of fatty acids for Belgian women, focused on n-6 and n-3 polyunsaturated fatty acids

The intake of fat, saturated and monounsaturated FA (SFA and MUFA), and omega-6 and omega-3 PUFA has been estimated in 641 Belgian women (age 18-39 y). Their food intake was recorded using a 2-d food diary. The PUFA included were linoleic (LA), alpha-linolenic (LNA), arachidonic (AA), eicosapentaeonoic (EPA), docosapentaenoic (DPA) and docosahexaenoic (DHA) acids. The mean total fat intake corresponded to 34.3% of total energy intake (E). The mean intake of the FA groups corresponded to 13.7%, 13.1%, and 6.0% of E, for SFA, MUFA, and PUFA, respectively. The mean intake of LA was 5.3% of E and of LNA was 0.6% of E, with a mean LA/LNA ratio of 8.7. The mean intake of AA was 0.03% of E. The mean intake of EPA, DPA, and DHA was 0.4%, 0.01%, and 0.06% of E, respectively. According to the Belgian recommendations, the total fat and SFA intake was too high for about three-quarters of the population. The mean LA and overall n-6 PUFA intake corresponded with the recommendation, with part of the population exceeding the upper level. Conversely, the population showed a large deficit for LNA and n-3 PUFA. The major food source for LA and LNA was fats and oils, followed by cereal products. The main sources of long-chain PUFA were fish and seafood, and meat, poultry, and eggs. From a public health perspective, it seems desirable to tackle the problem of low n-3 PUFA intake.     

Spectrum mobility management in cognitive two‐tier networks

Recently, new type of small Base Station known as “femtocell” has emerged. Femtocells are deployed by customers with minimal or no radio frequency planning in arbitrary locations. Thus, operators must use new approaches rather than the classic network planning and optimization. Self‐organization techniques will allow femtocells to integrate themselves into the network, learn about their environment, and adjust their parameters (power, frequency) accordingly. In this paper, a new spectrum mobility management algorithm is proposed. It allows intelligent use of the spectrum by secondary user (femtocell guest user) accessing spectrum holes unoccupied by primary users (subscriber user) and handing over to new channels or femtocells when primary user appears. Our solution aims to have more adaptive and aware communication system, which can make better use of available natural resources.     

Iron-catalyzed oxidation of arsenic(III) by oxygen and by hydrogen peroxide: pH-dependent formation of oxidants in the Fenton reaction

The oxidation kinetics of As(III) with natural and technical oxidants is still notwell understood, despite its importance in understanding the behavior of arsenic in the environment and in arsenic removal procedures. We have studied the oxidation of 6.6 microM As(II) by dissolved oxygen and hydrogen peroxide in the presence of Fe(II,III) at pH 3.5-7.5, on a time scale of hours. As(III) was not measurably oxidized by O2, 20-100 microM H2O2, dissolved Fe(III), or iron(III) (hydr)-oxides as single oxidants, respectively. In contrast, As(III) was partially or completely oxidized in parallel to the oxidation of 20-90 microM Fe(II) by oxygen and by 20 microM H2O2 in aerated solutions. Addition of 2-propanol as an *OH-radical scavenger quenched the As(III) oxidation at low pH but had little effect at neutral pH. High bicarbonate concentrations (100 mM) lead to increased oxidation of As-(III). On the basis of these results, a reaction scheme is proposed in which H2O2 and Fe(II) form *OH radicals at low pH but a different oxidant, possibly an Fe(IV) species, at higher pH. With bicarbonate present, carbonate radicals might also be produced. The oxidant formed at neutral pH oxidizes As(III) and Fe(II) but does not react competitively with 2-propanol. Kinetic modeling of all data simultaneously explains the results quantitatively and provides estimates for reaction rate constants. The observation that As(III) is oxidized in parallel to the oxidation of Fe(II) by O2 and by H2O2 and that the As(III) oxidation is not inhibited by *OH-radical scavengers at neutral pH is significant for the understanding of arsenic redox reactions in the environment and in arsenic removal processes as well as for the understanding of Fenton reactions in general.