The 837 keV resonance is used for the rapid and non-destructive determination of the gradient of fluorine on the surface of metallic samples. The precise yield curve of this resonance for thick target and the experimental sensitivity of the method have been determined. With this method less than 5·10?4 μg·cm?2 fluorine content can be measured. The resolution is of the order of 1000 Å in aluminium and the concentration profiles can be measured to the depth of 1 μm. The time requirement of a surface analysis is 15–30 min, and 2–3 hrs of a gradient measurement. In addition, this method is simpler and more sensitive than the detection of the 1350 keV alpha-particles from the19F(p, αo)16O reaction. 相似文献
The experimental device used is described. Excitation functions are given for an angle of observation 150° with respect to
the incident beam. The possibilities of applying these reactions to the measurement of surface lithium and fluorine concentrations
are considered. The detection limits for these two elements are shown to be 5·10−3 μg·cm−2 with protons of energy between 1,350 and 1,500 keV. The method is compared with that based on the detection of prompt γ-rays
from the reactions7Li(p, γ)8Be and19F(p, α γ)16O.
相似文献
Electron impact mass spectrometry has been used together with linked scans, exact mass measurements and mass-analysed ion kinetic energy spectrometry to study nine inacrocyclic polyether lactones in detail. The presence of abundant hydrogenated oxirane ions has been observed for all the compounds examined, and confirmed by kinetic energy release measurements. 相似文献
The (γ, n) activation curves for 17 elements were determined as a function of energy between 25 and 42 MeV. From these are
deduced the detection sensitivities intrinsically possible for an average beam intensity of 100 μA. Our experimental results
are compared with values calculated byG. J. Lutz. The activation curves relative to certain competitive nuclear reactions on N, O and Na, liable to interfere in the measurements
of C, N and F, were also determined. It is shown that the relative importance of these competitive nuclear reactions decreases
rapidly for energies below 30 MeV and becomes practically negligible at 25 MeV.
相似文献
Static pressure usually increases the transition temperatures of polymers by decreasing their free volume. If the pressurizing medium is soluble in the polymer matrix, the opposing effect of increasing the free volume is possible. Those shifts of transition temperatures were monitored with a medium-pressure Differential Scanning Calorimetry (DSC) device. The influences of sorbed and surrounding gas molecules are demonstrated by changes occurring in the transition temperature regions. The results show the severe plasticizing effect of CO2 on poly(p-phenylene sulphide) (PPS). The glass transition temperature TG and the temperature of crystallization TC are influenced by sorbed gas molecules. They decrease due to sorbed CO2 molecules. Glass transition is lowered, but is difficult to interpret, as relaxation phenomena which diminish with increasing pressure occur during DSC runs. In crystallites no gas solution is usually possible, so that the melting point of PPS is mainly affected by influences other than plasticization. 相似文献
Tetrafluoroaurates(III) of Lanthanoides M2F[AuF4]5 (M = Tb, Dy, Ho, Er) Tetrafluoroaurates(III) M2F[AuF4]5 with M = Tb, Dy, Ho, Er, all yellow, have been obtained. From single crystal data they crystallize triclinic, space group P1 -C1i (No. 2) with Tb: a = 1 194,34(7) pm, b = 798,46(6) pm, c = 902,02(7) pm, α = 89,033(7)°, β = 88,990(6)°, γ = 89,006(7)°; Dy: a = 1 191,66(9) pm, b = 796,33(8) pm, c = 899,65(9) pm, α = 88,956(8)°, β = 89,056(8)°, γ = 88,972(8)°; Ho: a = 1 189,06(10) pm, b = 795,46(6) pm, c = 896,81(7) pm, α = 88,912(8)°, β = 89,101(7)°, γ = 88,873(8)°; Er: a = 1 185,20(40), b = 793,98(14), c = 893,83(20), α = 88,751(23)°, β = 89,187(26)°, γ = 88,884(9)° 相似文献
A high-precision exact-matching quadruple isotope dilution method (ID4MS) was employed for the quantitation of nitrate in an air-dried spinach powder Certified Reference Material (CRM). The analyte was extracted in hot water following addition of 15NO\({}_{3}^{-}\) internal standard. The blend was then treated with sulfamic acid to remove nitrite and with triethyloxonium tetrafluoroborate to promote aqueous conversion of nitrate into volatile EtONO2. The derivative was analyzed by headspace GC–MS with 3-min elution time. The method performance was validated with a series of tests which demonstrated adequate selectivity and ruggedness. This method supported the development of novel SPIN-1 CRM giving a modest contribution to its uncertainty (uchar = 0.85%). With respect to previous attempts, the SPIN-1 was proven stable, homogeneous (uhom = 0.44%), and suitable for spinach monitoring under EU regulations. On dried basis, the nitrate content of SPIN-1 was found to be 22.53 ± 0.43 mg/g (Uc = 1.9%, k = 2). The material was also used in an inter-laboratory study where four laboratories employed a total of ten measurement methods.
Ultrasmall gold nanoparticles (diameter about 2 nm) were surface-functionalized with cysteine-carrying precision macromolecules. These consisted of sequence-defined oligo(amidoamine)s (OAAs) with either two or six cysteine molecules for binding to the gold surface and either with or without a PEG chain (3400 Da). They were characterized by 1H NMR spectroscopy, 1H NMR diffusion-ordered spectroscopy (DOSY), small-angle X-ray scattering (SAXS), and high-resolution transmission electron microscopy. The number of precision macromolecules per nanoparticle was determined after fluorescent labeling by UV spectroscopy and also by quantitative 1H NMR spectroscopy. Each nanoparticle carried between 40 and 100 OAA ligands, depending on the number of cysteine units per OAA. The footprint of each ligand was about 0.074 nm2 per cysteine molecule. OAAs are well suited to stabilize ultrasmall gold nanoparticles by selective surface conjugation and can be used to selectively cover their surface. The presence of the PEG chain considerably increased the hydrodynamic diameter of both dissolved macromolecules and macromolecule-conjugated gold nanoparticles. 相似文献
Two new families of N,O-nucleoside analogues containing the anthracene moiety introduced through the nitrosocarbonyl ene reaction with allylic alcohols were prepared. The core structure is an isoxazolidine heterocycle that introduces either atom either a phenyl ring or dimethyl moiety at the C3 carbon. Different heterobases were inserted at the position 5 of the heterocyclic ring. One of the synthesized compounds demonstrated a good capacity to induce cell death and an appreciable nuclear fragmentation was evidenced in treated cells. 相似文献