Instant conversion of air to a clathrate hydrate: CO(2) hydrates directly from moist air and moist CO(2)(g)

The rapid conversion of vapor mixtures containing the gases CO(2), H(2)S, and HCN to clathrate hydrates was reported recently. The novel method is based on the pulsing of warm vapor mixtures, including a carrier gas, into a cold condensation chamber. With cooling, the vapors, which also include ～1% water and either tetrahydrofuran or trimethylene oxide as a catalyst, nucleate aqueous solution nanodroplets that, on a millisecond time scale, crystallize as hydrate nanoparticles that consume 100% of the water. Humid air approximates the content of mixtures used successfully in the vapor-to-hydrate conversions. FTIR spectra are examined for gas hydrates formed directly from air and air enriched with CO(2), as well as hydrate particles for which CO(2)(g) serves as both guest and aerosol medium. In each instance all of the water in the condensed phase converts to a clathrate hydrate. The subsecond ether-catalyzed formation of the hydrates near 230 K requires only a few percent of the CO(2) pressure used in conventional processes that yield fractional amounts of gas hydrates on an hour time scale in the same temperature range.     

On corner flows of Oldroyd-B fluids

Exact series solutions for planar creeping flows of Oldroyd-B fluids in the neighbourhood of sharp corners are presented and discussed. Both reentrant and non-reentrant sectors are considered. For reentrant sectors it is shown that more than one type of series solution can exist formally, one type exhibiting Newtonian-like asymptotic behaviour at the corner, away from walls, and another type exhibiting the same kind of asymptotics as an Upper Convected Maxwell (UCM) fluid. The solutions which are Newtonian-like away from walls are shown to develop non-integrable stress singularities at the walls when the no-slip velocity boundary condition is imposed. These mathematical solutions are therefore inadmissible from the physical viewpoint under no-slip conditions. An inadmissible solution, with stress singularities which are not everywhere integrable, is identified among the solutions of UCM-type. For a 270° reentrant sector the radial behaviour of the normal stress is everywhere r^−0.613. In the viscometric region near a wall, the radial normal stress σ^rr behaves like (rε)^−0.613, where ε is the angle made with the wall. In addition σ^rθ is infinite (not integrable) at the wall even when r is non-zero. Another UCM-type solution has a normal stress behaviour away from walls which is r^−0.985 for 270° sector. Again, this solution has a non-integrable stress singularity and is therefore inadmissible. Finally, for non-reentrant sectors it is shown that the flow is always Newtonian-like away from walls.     

A weak version of ◊ which follows from 2ℵ 0<2ℵ 1

We prove that if CH holds (or even if 2^ℵ ₀ < 2^ℵ ₁), then a weak version of ◊ holds. This weak version of ◊ is a ◊-like principle, and is strong enough to yield some of the known consequences of ◊. The second author wishes to thank the United States-Israel Binational Foundation for partially supporting his research by Grant 1110.     

The consistency with CH of some consequences of Martin’s axiom plus2^{\aleph _0 } > \aleph _1

We present here a (weak) axiom which implies some of the consequences of MA, but is consistent with GCH. We use the method of Jensen in his proof of consis (ZFC+GCH+SH). The third author wishes to thank the United States—Israel Binational Foundation for partially supporting this research by Grant 1110.     

A stability result using the matrix norm to bound the permanent

We prove a stability version of a general result that bounds the permanent of a matrix in terms of its operator norm. More specifically, suppose A is an n × n matrix over C (resp. R), and let P denote the set of n × n matrices over C (resp. R) that can be written as a permutation matrix times a unitary diagonal matrix. Then it is known that the permanent of A satisfies |per(A)| ≤ ||A|| ⁿ ₂ with equality iff A/||A||₂ ∈ P (where ||A||₂ is the operator 2-norm of A). We show a stability version of this result asserting that unless A is very close (in a particular sense) to one of these extremal matrices, its permanent is exponentially smaller (as a function of n) than ||A|| ⁿ ₂. In particular, for any fixed α, β > 0, we show that |per(A)| is exponentially smaller than ||A|| ⁿ ₂ unless all but at most αn rows contain entries of modulus at least ||A||₂(1?β).     

High-spin states in the T z = −1/2 nucleus 55Ni

High-spin states of the isospin T _z = ? 1/2 nucleus ⁵⁵Ni have been identified for the first time by means of the reaction ²⁸Si(³⁶Ar,2αn) at 143 MeV beam energy. The Gammasphere array together with ancillary detectors was used to detect γ rays in coincidence with evaporated light particles. The level scheme of ⁵⁵Ni comprising four transitions is compared to its mirror partner ⁵⁵Co and shell-model calculations in the fp shell.     

Magnetically modified single and turbostratic stacked graphenes from tris(2,2'-bipyridyl) iron(II) ion-exchanged graphite oxide

Loading of graphite oxide (GO) with tris(2,2'-bipyridyl) iron(II) ions and subsequent calcination affords a novel graphene-based composite with magnetic and electrically conductive properties. The pH of the starting aqueous suspension and the washing procedure play a crucial role in the successful immobilization of the iron precursor, which is mainly governed by ion exchange. The complex is intercalated between the graphene oxide layers, where it adopts a distorted conformation. Rapid heating of this solid results in the deflagration of GO and the formation of ultrafine ( d = 2-14 nm) Fe2O3 particles with maghemite as the dominant phase. The superparamagnetic maghemite crystals are dispersed uniformly in the high-surface-area diamagnetic matrix built up from single or turbostratic stacked graphenes.     

A membrane introduction flame ionization/electron capture detection (MIFID/ECD) system for the rapid, real-time screening of volatile disinfection byproducts and hydrocarbon contaminants in water

Described is a system that employs an online membrane introduction (MI) interface coupled with parallel flame ionization and electron capture detectors (FID/ECD). We report the use of a MIFID/ECD system as an online method to detect total volatile organic halides (ΣVOXs) and volatile organic compounds (ΣVOCs) as aggregate parameters in environmental water samples at sub parts-per-billion levels without the need for sample handling or analyte pre-concentration. The instrument provides rapid screening and real-time monitoring capabilities of important classes of water contaminants in a simple system without the vacuum requirements of MS detectors. Furthermore, the MIFID/ECD instrument was successfully employed as a real-time reaction monitor for the photodegradation of toluene by an advanced oxidation process and the formation of volatile disinfection byproducts in the chlorination of natural waters. The results of these experiments compare favorably to those obtained using membrane introduction mass spectrometry (MIMS).