Precision Rosenbluth measurement of the proton elastic form factors

We report the results of a new Rosenbluth measurement of the proton electromagnetic form factors at Q2 values of 2.64, 3.20, and 4.10 GeV2. Cross sections were determined by detecting the recoiling proton, in contrast to previous measurements which detected the scattered electron. Cross sections were determined to 3%, with relative uncertainties below 1%. The ratio mu(p)G(E)/G(M) was determined to 4%-8% and showed mu(p)G(E)/G(M) approximately 1. These results are consistent with, and much more precise than, previous Rosenbluth extractions. They are inconsistent with recent polarization transfer measurements of similar precision, implying a systematic difference between the techniques.     

Dielectric and proton relaxation from ammonium ion motion in alum

Dielectric losses and proton spin lattice relaxation T₁ and T_1? give identical correlation times in NH₄Al(SO₄)₂ · 12H₂O from 75 to 200 K. This is explained as hopping of NH⁺₄ between two positions with different orientations and electric dipole moments.     

Interactions between hydrogen isotopes and carbon monoxide on rhenium

The rate of absorption by a clean rhenium filament of carbon monoxide and deuterium from a mixture of the two gases was little different in the early stages from that of the two gases individually. However, continued exposure of the deuterium-covered filament to carbon monoxide led to ready replacement, the sticking probability of carbon monoxide being about 80% of its value on a clean filament. A similar experiment with a hydrogen deuteride-covered filament led to a gas phase hydrogen isotope composition consistent with dissociative adsorption of hydrogen deuteride.     

Strontium dicobalt orthophosphate

In crystalline SrCo₂(PO₄)₂; triclinicP¯1,M _r =395.4,a=5.014(2),b=8.639(4),c=9.691(1)Å,a=118.04(3),=75.09(4), =86.90(4)°,V=350.4(3)ų,Z=2,D _calc=3.747 g cm^–3, MoK=0.71069 Å,=12.49 mm^–1,F(000)=372,T=298 K,R=4.1% for 1190 obs. reflections; Co²⁺ and PO ₄ ^3– ions are found on planes parallel to (001). Co²⁺ occupies sites of four- and five-(trigonal bipyramidal) coordination with average Co-O distances, 1.948(8) and 2.087(8) Å, respectively. The blue color of solid is due to the tetrahedral coordination geometry of the four-coordinate copper atoms.     

Triaquocalcium(18-crown-6) heptaiodopentacuprate(I), triaquostrontium(18-crown-6) heptaiodopentacuprate(I), and triaquozinc(18-crown-6) heptaiodopentacuprate(I)

Ca(H₂O)₃(18-crown-6)Cu₅I₇ (I), Sr(H₂O)₃(18-crown-6)Cu₅I₇ (II), and Zn(H₂O)₃(18-crown-6)Cu₅I₇ (III) are isostructural solids with a polymeric array of Cu₅I₇ stoichiometry. The repeat unit may be understood as a distorted tetrahedron of four copper(I) atoms, bridged on two faces and three edges by iodide atoms, bridged on an additional edge by an I–Cu–I sequence and linked in polymeric series by this copper atom and one of the face-bridging iodide atoms. The three solid materials display no emission in the visible when excited in the ultraviolet. Comparison with other polymeric cuprous iodide materials that do emit suggests that the quenching of the expected emission may stem from short Cu–Cu interactions (2.4–2.5 Å) that represent a bonding interaction.     

How often are chaotic transients in spatially extended ecological systems?

A traditional assumption in quantitative ecology is that the asymptotic state of the model determines what can be observed in the evolution of the system. It is suggested, however, that irregular transient behaviors may be more relevant than the long term behaviors. Here we investigate how often transient dynamics can be expected in spatially extended ecological systems. Our study suggests that although chaotic transient dynamics indeed exist, sustained dynamics may be more prevalent than transient ones due to the high dimensionality of such systems.     

New enzyme sensors for morphine and codeine based on morphine dehydrogenase and laccase

Two new enzymatic methods have been developed to quantify morphine and codeine simultaneously in a flow injection system (FIA). The first enzyme sensor for morphine or codeine is based on immobilizing morphine dehydrogenase (MDH) and salicylate hydroxylase (SHL) on top of a Clark-type oxygen electrode. Morphine or codeine oxidation by MDH leads to a consumption of oxygen by SHL via the production of NADPH. This decreases the oxygen current of the Clark electrode. Concentrations of codeine and morphine are detected between 2 and 1000 μM and between 5 and 1000 μM, respectively. The second enzyme sensor for morphine is based on laccase (LACC) and PQQ-dependent glucose dehydrogenase (GDH) immobilized at a Clark oxygen electrode. Morphine is oxidized by laccase under consumption of oxygen and regenerated by glucose dehydrogenase. Since laccase cannot oxidize codeine, this sensor is selective for morphine. Morphine is detected between 32 nM and 100 μM. Both sensors can be operated simultaneously in one flow system (FIA) giving two signals without the requirement for a separation step. This rapid and technically simple method allows discrimination between morphine and codeine in less than 1 min after injection. The sampling rate for quantitative measurements is 20 h^–1. The method has been applied to the quantitative analysis of codeine or morphine in drugs. Received: 10 August 1998 / Revised: 29 January 1999 / Accepted: 5 February 1999     

Selective retardation of perfume oil evaporation from oil-in-water emulsions stabilized by either surfactant or nanoparticles

We have used dynamic headspace analysis to investigate the evaporation rates of perfume oils from stirred oil-in-water emulsions into a flowing gas stream. We compare the behavior of an oil of low water solubility (limonene) and one of high water solubility (benzyl acetate). It is shown how the evaporation of an oil of low water solubility is selectively retarded and how the retardation effect depends on the oil volume fraction in the emulsion. We compare how the evaporation retardation depends on the nature of the adsorbed film stabilizing the emulsion. Surfactant films are less effective than adsorbed films of nanoparticles, and the retardation can be further enhanced by compression of the adsorbed nanoparticle films by preshrinking the emulsion drops.