Cumulant functions in optical coherence theory

Cumulant functions are introduced to describe the statistical state of a radiation field. These functions are simply related to the optical coherence functions but have some interesting features. It is shown that if the cumulant functions of all orders greater than some numberN ₀ vanish then they also vanish for all orders greater than 2. Thermal field is the only field having this property. This property holds whether the field is described by a classical stochastic process or by a quantum density operator. Further the particular operator ordering used in defining these cumulant functions for the quantized field affects only the second order cumulant function. To describe the statistical state of a vector field such as partially polarized or unpolarized radiation, one would need to introduce cumulant tensors.     

Gas phase activation energy for unimolecular dissociation of biomolecular ions determined by focused RAdiation for gaseous multiphoton ENergy transfer (FRAGMENT)

We present a novel approach for the determination of activation energy for the unimolecular dissociation of a large (>50 atoms) ion, based on measurement of the unimolecular dissociation rate constant as a function of continuous-wave CO(2) laser intensity. Following a short ( approximately 1 s) induction period, CO(2) laser irradiation produces an essentially blackbody internal energy distribution, whose 'temperature' varies inversely with laser intensity. The only currently available method for measuring such activation energies is blackbody infrared radiative dissociation (BIRD). Compared with BIRD, FRAGMENT: (a) eliminates the need to heat the surrounding ion trap and vacuum chamber to each of several temperatures (each requiring hours for temperature equilibration); (b) offers a three-fold wider range of effective blackbody temperature; and (c) extends the range of applications to include initially cold ions (e.g., gas-phase H/D exchange). Our FRAGMENT-determined activation energy for dissociation of protonated bradykinin, 1.2 +/- 0.1 eV, agrees within experimental error to the value, 1.3 +/- 0.1 eV, previously reported by Williams et al. from BIRD experiments. Copyright 1999 John Wiley & Sons, Ltd.     

Using the solvation parameter model to characterize functionalized ionic liquids containing the tris(pentafluoroethyl)trifluorophosphate (FAP) anion

Ionic liquids (ILs) containing the tris(pentafluoroethyl)trifluorophosphate anion [FAP]⁻ have attracted increased attention due to their unique properties including ultrahigh hydrophobicity, hydrolytic stability, and wide electrochemical window. In this study, the solvation parameter model is used via gas chromatography to characterize the solvation interactions of seven ILs containing amino, ester, and hydroxyl functional groups appended to the cation and paired with [FAP]⁻, as well as three ILs containing the bis[(trifluoromethyl)sulfonyl]imide anion [NTf₂]⁻. The role of the functional groups, nature of the counter anion, and cation type on the system constants were evaluated. ILs containing [FAP]⁻ possessed lower hydrogen bond basicity than NTf₂-based ILs having the same cationic component; in the case of hydroxyl-functionalized cations, the presence of [FAP]⁻ led to an enhancement of the hydrogen bond acidity, relative to the NTf₂-analogs. The system constants support the argument that [FAP]⁻ weakly coordinates the cation and any appended functional groups, promoting properties of the cation which might be masked by stronger interactions with other anion systems. The chromatographic performance of the IL stationary phases was evaluated by examining the retention behavior and separation selectivity for chosen analytes. The results from this work can be used as a guide for choosing FAP-based ILs capable of exhibiting desired solvation properties while retaining important physical properties including high thermal stability and high hydrophobicity. Figure In this study, the solvation parameter model is used via gas chromatography to characterize the solvation interactions of seven ILs containing amino, ester, and hydroxyl functional groups appended to the cation and paired with tris(pentafluoroethyl)trifluorophosphate [FAP]⁻, as well as three ILs containing the bis[(trifluoromethyl)sulfonyl]imide anion [NTf₂]⁻. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Isolation and identification of two new seco-cembranoids from cigarette smoke

The isolation and identification from cigarette smoke condensate of 5-isopropyl-8,12-dimethyl-3$\text{E}$,8$\text{E}$,12$\text{E}$,l4-pentadecatetraen-2-one and its 12$\text{Z}$ isomer are reported.     

Precipitation of a dioxouranium(VI) species from a room temperature ionic liquid medium

The novel complex 1-butyl-3-methylimidazolium mu(4)-(O,O,O',O'-ethane-1,2-dioato)-bis[bis(nitrato-O,O)dioxouranate(VI)] (1) has been precipitated from a room-temperature ionic liquid medium containing 1-butyl-3-methylimidazolium nitrate, nitric acid, and acetone. X-ray analysis of complex 1 shows the unit cell contains four [C(4)mim](+) cations and two independent [[UO(2))(NO(3))(2)](2)(mu(4)-C(2)O(4))](2-) moieties, both of which are located about inversion centers. The [C(4)mim](+) cations are arranged such that they produce large channels in which the anions are located. This arrangement of [[(UO(2))(NO(3))(2)](2)(mu(4)-C(2)O(4))](2-) groups is unique to this compound. Crystal data for compound 1: M = 1154.56, monoclinic, space group P2(1)/c, a = 15.452(2) A, b = 20.354(3) A, c = 10.822(4) A, beta = 106.84(2) degrees, U = 3258(1) A(-)(3), Z = 4, mu = 10.023 mm(-1), R(int) = 0.0788.     

Functionalized electrospun nanofibers as bioseparators in microfluidic systems

Functionalized electrospun nanofibers were integrated into microfluidic channels to serve as on-chip bioseparators. Specifically, poly(vinyl alcohol) (PVA) nanofiber mats were shown to successfully serve as bioseparators for negatively charged nanoparticles. Nanofibers were electrospun onto gold microelectrodes, which were incorporated into poly(methyl methacrylate) (PMMA) microfluidic devices using UV-assisted thermal bonding. PVA nanofibers functionalized with poly(hexadimethrine bromide) (polybrene) were positively charged and successfully filtered negatively charged liposomes out of a buffer solution, while negatively charged nanofibers functionalized with Poly(methyl vinyl ether-alt-maleic anhydride) (POLY(MVE/MA)) were shown to repel the liposomes. The effect of fiber mat thickness was studied using confocal fluorescence microscopy, determining a quite broad optimal range of thicknesses for specific liposome retention, which simplifies fiber mat production with respect to retention reliability. Finally, it was demonstrated that liposomes bound to positively charged nanofibers could be selectively released using a 4-(2-Hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES)-sucrose-saline (HSS) solution of pH 9, which dramatically changes the nanofiber zeta potential and renders the positively charged nanofibers negatively charged. This is the first demonstration of functional electrospun nanofibers used to enable sample preparation procedures of isolation and concentration in lab-on-a-chip devices. This has far reaching impact on the ability to integrate functional surfaces and materials into microfluidic devices and to significantly expand their ability toward simple lab-on-a-chip devices.     

Beurteilung verschiedener Fehler an Hand eines Ringversuches zur Bestimmung von Stickstoff in St?hlen

Zusammenfassung Ringversuche zur Bestimmung niedriger Stickstoffgehalte von Stählen ergaben im Vergleich zu den Wiederholstreuungen der einzelnen Laboratorien relativ hohe Vergleichsstreuungen, die auf systematische Fehler zwischen den Laboratorien zurückzuführen sind. Es wurde daher versucht, diese Fehler in materialunabhängige und materialabhängige Komponenten aufzuschlüsseln. Die Ermittlung der materialunabhängigen Fehler erfolgte an Hand von Ausgleichsgeraden zwischen den Mittelwerten jedes Laboratoriums und den gemeinsamen Mittelwerten aller Laboratorien. Die unterschiedlichen Ordinatenabschnitte dieser Geraden erlauben einen Rückschluß auf die verschiedenen Blindwerte, die verschiedenen Steigungen weisen auf unterschiedliche Empfindlichkeiten der Laboratorien hin.Die Untersuchung der materialabhängigen Fehler (Wechselwirkungen) erfolgte einerseits durch paarweisen Vergleich von Proben nach Youden, andererseits durch Prüfung der Abweichungen einzelner Werte von den Ausgleichsgeraden.Eine solche Analyse der Art der systematischen Fehler erlaubt auch einen Rückschluß auf ihre Ursachen, was aus der wenig aussagekräftigen Vergleichsstreuung nicht möglich ist.

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Assessment of errors from round-robin results for the determination of nitrogen in steels

Summary Round-robin tests for the determination of low nitrogen contents in steels showed a much worse reproducibility as compared to the repeatability. This observation is due to systematic errors between the laboratories. An attempt was therefore made to distinguish between materialindependent and material-dependent systematic errors.In order to evaluate the material-independent errors, the mean values from each laboratory were plotted against the total average from all laboratories and regresssion lines were drawn between the points for each laboratory.Different y-intercepts of these regression lines indicate different blanks, whereas differences in the slope account for differences in calibration.The material-dependent errors (interaction effects) were examined on the one hand by comparing pairs of samples as described by Youden, and on the other hand by the abnormal deviations of certain samples from the regression lines of the respective laboratory.This kind of graphic or mathematical evaluation makes it possible to identify the kind of error, which is not possible from reproducibility data.

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Die Verfasser danken den Herren Univ. Prof. Dr. F. J. Schnitzer und Univ. Doz. Dr. G. Kopetzky für ihre Anregungen und die kritische Durchsicht der Arbeit.