Rapid, Specific Determination of Iodine and Iodide by Combined Solid-Phase Extraction/Diffuse Reflectance Spectroscopy

A new, rapid methodology for trace analysis using solid-phase extraction is described. The two-step methodology is based on the concentration of an analyte onto a membrane disk and on the determination by diffuse reflectance spectroscopy of the amount of analyte extracted on the disk surface. This method, which is adaptable to a wide range of analytes, has been used for monitoring ppm levels of iodine and iodide in spacecraft water. Iodine is used as a biocide in spacecraft water. For these determinations, a water sample is passed through a membrane disk by means of a 10-mL syringe that is attached to a disk holder assembly. The disk, which is a polystyrene−divinylbenzene composite, is impregnated with poly(vinylpyrrolidone) (PVP), which exhaustively concentrates iodine as a yellow iodine−PVP complex. The amount of concentrated iodine is then determined in only 2 s by using a hand-held diffuse reflectance spectrometer by comparing the result with a calibration curve based on the Kubelka−Munk function. The same general procedure can be used to determine iodide levels after its facile and exhaustive oxidation to iodine by peroxymonosulfate (i.e., Oxone reagent). For samples containing both analytes, a two-step procedure can be used in which the iodide concentration is calculated from the difference in iodine levels before and after treatment of the sample with peroxymonosulfate. With this methodology, iodine and iodide levels in the 0.1−5.0 ppm range can be determined with a total workup time of ∼60 s with a RSD of ∼6%

The Evolution of Reaction-diffusion Controllers for Minimally Cognitive Agents

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Rapid, Low Level Determination of Silver(I) in Drinking Water by Colorimetric–solid-phase Extraction

A rapid, highly sensitive two-step procedure for the trace analysis of silver(I) is described. The method is based on: (1) the solid-phase extraction (SPE) of silver(I) from a water sample onto a disk impregnated with a silver-selective colorimetric reagent, and (2) the determination of the amount of complexed analyte extracted by the disk by diffuse reflectance spectroscopy (DRS). This method, called colorimetric–solid-phase extraction (C–SPE), was recently shown effective in determining low concentrations (0.1–5.0 mg/ml) of iodine and iodide in drinking water. This report extends C–SPE to the trace (∼4 μg/l) level monitoring of silver(I) which is a biocide used on the International Space Station (ISS). The determination relies on the manually driven passage of a water sample through a polystyrene–divinylbenzene disk that has been impregnated with the colorimetric reagent 5-(p-dimethylaminobenzylidene) rhodanine (DMABR) and with an additive such as a semi-volatile alcohol (1,2-decanediol) or nonionic surfactant (Brij 30). The amount of concentrated silver(I) is then determined in a few seconds by using a hand-held diffuse reflectance spectrometer, with a total sample workup and readout time of ∼60 s. Importantly, the additive induces the uptake of water by the disk, which creates a local environment conducive to silver(I) complexation at an extremely high concentration factor (∼800). There is no detectable reaction between silver(I) and impregnated DMABR in the absence of the additive. This strategy represents an intriguing new dimension for C–SPE in which additives, directly loaded in the disk material, provide a means to manipulate the reactivity of the impregnated reagent

AN INNOVATIVE VISCOELASTIC TREATMENT FOR THE INTERNAL NOISE REDUCTION IN A REGIONAL AIRCRAFT

The improvement of interior comfort is becoming an increasingly required target in the transport engineering field, with particular attention to the aviation one. Generally, an aircraft is affected by several noise sources, from the engine power unit to the broadband components, related to the turbulent boundary layer (TBL). In this contest, the leading industries, in cooperation with research centers and universities, are actually employed in the development of innovative passive/active solutions for the internal noise as well as vibrations control: such technological implications must, on the one hand, satisfy these design requirements as well as meet the current airworthiness regulations. The paper deals with the vibro-acoustic testing activity on a typical turboprop fuselage subjected to different external load conditions: the damping ratio and the transmission loss characterization has been performed for several materials, including two innovative viscoelastic treatments too. The results highlighted a very good behaviour of the novel viscoelastic foams in terms of both acoustic and thermal performance when compared to standard blanket supported by extra viscoelastic treatments offering a very interesting self-embedded solution with a good weight to performance ratio

Experimental and numerical assessment of innovative damping foams

The automotive industry is currently experiencing relevant technology changes in the design of the engines, transmission and total drivetrain, induced by increasing customer demand for fuel efficiency and more stringent government requirements in emissions and safety. One of the problems relating to environmental impact concerns the noise emitted by the vehicle, for which various solutions have been experimented: new and more resistant materials have been worked out in order to minimize noise pollution and the environmental impact of the vehicle, even at the end of the operating life of its components. This research illustrates a solution as a response to those requirements, as well as being a response to the targets of comfort: a viscoelastic material, appointed to increase the damping of structures involved in vibroacoustic phenomena generated in a vehicle. The performance of these innovative materials have been analyzed both from a numerical standpoint that experimental. Starting from the empirical results of tests carried out in the laboratory, finite element models have been developed in order to have a suitable numerical database for further vibro-acoustic simulations

SUMOylation determines the voltage required to activate cardiac IKs channels.

IKs channels open in response to depolarization of the membrane voltage during the cardiac action potential, passing potassium ions outward to repolarize ventricular myocytes and end each beat. Here, we show that the voltage required to activate IKs channels depends on their covalent modification by small ubiquitin-like modifier (SUMO) proteins. IKs channels are comprised of four KCNQ1 pore-forming subunits, two KCNE1 accessory subunits, and up to four SUMOs, one on Lys424 of each KCNQ1 subunit. Each SUMO shifts the half-maximal activation voltage (V1/2) of IKs ∼ +8 mV, producing a maximal +34-mV shift in neonatal mouse cardiac myocytes or Chinese hamster ovary (CHO) cells expressing the mouse or human subunits. Unexpectedly, channels formed without KCNE1 carry at most two SUMOs despite having four available KCNQ1-Lys424 sites. SUMOylation of KCNQ1 is KCNE1 dependent and determines the native attributes of cardiac IKs in vivo

Antiferromagnetic phase of the gapless semiconductor V3Al

Discovering new antiferromagnetic compounds is at the forefront of developing future spintronic devices without fringing magnetic fields. The antiferromagnetic gapless semiconducting D03 phase of V3Al was successfully synthesized via arc-melting and annealing. The antiferromagnetic properties were established through synchrotron measurements of the atom-specific magnetic moments, where the magnetic dichroism reveals large and oppositely-oriented moments on individual V atoms. Density functional theory calculations confirmed the stability of a type G antiferromagnetism involving only two-third of the V atoms, while the remaining V atoms are nonmagnetic. Magnetization, x-ray diffraction and transport measurements also support the antiferromagnetism. This archetypal gapless semiconductor may be considered as a cornerstone for future spintronic devices containing antiferromagnetic elements.Comment: Accepted to Physics Review B on 02/23/1

Weakly Coupled Motion of Individual Layers in Ferromagnetic Resonance

We demonstrate a layer- and time-resolved measurement of ferromagnetic resonance (FMR) in a Ni81Fe19 / Cu / Co93Zr7 trilayer structure. Time-resolved x-ray magnetic circular dichroism has been developed in transmission, with resonant field excitation at a FMR frequency of 2.3 GHz. Small-angle (to 0.2 degree), time-domain magnetization precession could be observed directly, and resolved to individual layers through elemental contrast at Ni, Fe, and Co edges. The phase sensitivity allowed direct measurement of relative phase lags in the precession oscillations of individual elements and layers. A weak ferromagnetic coupling, difficult to ascertain in conventional FMR measurements, is revealed in the phase and amplitude response of individual layers across resonance.Comment: 22 pages, 6 figures submitted to Physical Review