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81.
Ch. Berthelot G. Carraro V. Verdingh 《Journal of Radioanalytical and Nuclear Chemistry》1980,60(2):443-451
A large number of toxic elements, including Th and U, in Scheldt and NBS river sediments, have been determined non-destructively
by high energy photon activation. The length of irradiation varies between 1.5 hours for short lived-nuclides and 7–18 hours
for long lived-nuclides. The induced activities are measured using a single open-ended coaxial Ge(Li) detector and the photopeak
integrations are calculated using the total peak area method and the Cutipie computer program after substraction of the intrinsic
background of the detector from each spectrum (Angela program). The photonuclear reactions and the best detection limits for
36 elements are indicated. 相似文献
82.
K. Ardhaoui J. Rogez A. Ben Chérifa M. Jemal P. Satre 《Journal of Thermal Analysis and Calorimetry》2006,86(2):553-559
Lanthanum-bearing silicate-oxyapatites or britholites, Ca10–xLax(PO4)6–x(SiO4)xO with 1≤x≤6, have been synthesized by solid state reaction
at high temperature. They were characterized by X-ray diffraction and IR spectroscopy.
Using two microcalorimeters, the heat of solution of these compounds have
been measured at 298 K in a solution of nitric and hydrofluoric acid. A strained
least squares method was applied to the experimental results to obtain the
solution enthalpies at infinite dilution, and the mixing enthalpy in two steps.
In the first step the mixing enthalpy obtained is referenced to the britholite
monosubstituted and to the oxysilicate. The mixing enthalpy referenced to
the oxyapatite and to the oxysilicate is then extrapolated. In order to determine
the enthalpies of formation of all the terms of the solution, thermochemical
cycles were proposed and complementary experiments were performed. The results
obtained show a decrease of the enthalpy of formation with the amount of Si
and La introduced in the lattice. This was explained by the difference in
the bond energies of (Ca–O, P–O) and (La–O, Si–O). 相似文献
83.
J. Kvasil I. N. Mikhailov R. Ch. Safarov B. Choriev 《Czechoslovak Journal of Physics》1978,28(8):843-856
Some generalizations of the model for odd nuclei suggested by Kerman are considered. The effects of phonon admixtures on matrix elements of Coriolis interaction are studied. Several schemes are considered for studying the role of non-adiabatic effects in the even-even core.One of the authors B. Ch. thanks L. A.Malov and V. O.Nesterenko for many discussions of some questions connected with the determination of the phonon-quasiparticle admixtures. 相似文献
84.
G. Dlubek J. Stejny Th. Lüpke D. Bamford K. Petters Ch. Hübner M. A. Alam M. J. Hill 《Journal of Polymer Science.Polymer Physics》2002,40(1):65-81
High‐quality positron lifetime measurements (70 million total counts) are reported for polyethylenes (PEs) of different crystallinities (Xc = 3–82%). The specific volumes of the crystalline and amorphous phases (Vc and Va, respectively) were estimated from density and wide‐angle X‐ray scattering (WAXS) experiments. Some samples (those with low values of Xc) were branched PEs, and those with high values of Xc were linear PEs for which Xc was varied with changes in the crystallization temperature. Both Vc and Va increase with decreasing Xc in the range 0% ≤ Xc ≤ 56% (the branched PEs) but are constant for Xc ≥ 56% (the linear PEs). The lifetime spectra were analyzed with the MELT and LIFSPECFIT routines. Artifacts that can appear in the spectrum analysis were checked via an analysis of computer‐generated spectra. Four lifetime components appeared in all of the PEs; the two long‐lived ones are attributed to pick‐off annihilation of ortho‐positronium (o‐Ps) in crystalline regions (τ3) and in holes of the amorphous phase (τ4). With increasing Xc, τ3 decreases from about 1.2 to 1 ns, τ4 decreases from 3.0 to 2.5 ns, and the intensity I4 decreases from 29 to 0%. An increase in I3 from 6 to 12% was observed. A comparison with simulations shows that the true I3 value approaches 0 for Xc → 0%. The decrease in I4 is weaker than the increase in Xc; this leads to the conclusion that the apparent specific o‐Ps yield in the amorphous phase I4Xc increases with Xc. Possible reasons for this surprising results are discussed. The fractional free hole volume [h = (Va ? Vocc)/Va, where Vocc is the crystalline occupied volume] was estimated from density and WAXS results. Between Xc = 0 and 56%, h decreases from 0.151 to 0.090, but it does not change further above Xc = 56%. The mean size (v) of the local free volumes (holes) estimated from τ4 decreases from 200 to 150 Å3. The number density of holes (Nh) calculated from these values (Nh = h/v) also decreases from 0.8 to 0.6 nm?3 in the range 0% ≤ Xc ≤ 56%. The values of Va, Vc, h, and Nh increase with an increasing degree of branching but do not vary for linear PEs. The possible influence of a crystalline–amorphous interfacial phase (three‐phase model) on the observed lifetime parameters is also discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 65–81, 2002 相似文献
85.
Summary The retention, enantionselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propionyl,-butyrul and-valeryl PP) on an 1-acid glycoprotein (AGP)-bonded column have been investigated by changing eluent composition (eluent pH, buffer concentration, type and content of organic modifier). The retention of these cationic solutes, PP and its ester derivatives, was influenced by eluent pH, ionic strength and organic modifier content. The enantioselectivity was dependent on eluent pH and type of organic modifier. Reversal of the enantiomeric elution order of ester derivatives of PP (O-propionyl-butyryl) and-valeryl PP) occurred around eluent pH 6–7. These results suggst that chiral recognition or binding properties may be altered by the change in eluent composition, espeically eluent pH and type of organic modifier. 相似文献
86.
Staszczuk P. Sternik D. Chądzyński G. W. 《Journal of Thermal Analysis and Calorimetry》2003,71(1):173-182
Using thermo-analytical and sorptometric methods physicochemical properties and especially surface heterogeneity of HgBa2Ca2Cu3O8+, (Hg-1223) was investigated. The desorption energy distribution was derived from mass loss Q-TG and differential mass loss Q-DTG curves of thermodesorption in quasi-isothermal conditions of pre-adsorbed n-octane and water vapour. It is shown that the superconducting Hg-1223 phase is highly sensitive to water vapours. The mechanism of water adsorption depends largely on the activation time. By water vapour saturation in a period of 90 min, physisorption takes place. Prolonged periods result in a chemical decomposition. From nitrogen ad- and desorption isotherms the fractal dimension of superconductors were calculated. A new approach is proposed to calculate fractal dimension from Q-TG curves.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
87.
Z. F. Ch. Kachani 《Fresenius' Journal of Analytical Chemistry》1965,213(6):427-430
Zusammenfassung Es wurde festgestellt, daß die Farbe einer Actinomycin C-Lösung in sehr engem Zusammenhang mit der Konzentration dieser Substanz in der Lösung steht. Die photometrisch ermittelte Farbabnahme geht mit dem durch mikrobiologischen Test bestimmten Aktivitätsverlust in vieler Hinsicht parallel. Bei der Aktivitätsabnahme spielt die Art des Lösungsmittels eine wichtige Rolle. Die stärkste Aktivitätsminderung nach dem Erhitzen wurde in bidest. Wasser, die geringste Aktivitätsabnahme in Glykokollpuffer beobachtet.
Summary The concentration of active actinomycin C in a solution can be determined quite simply by a photometric method. Comparison of results showed good agreement between the microbiological tests and the photometric method. Actinomycin C suffers most loss of activity by heating when dissolved in distilled water and least when dissolved in glycine buffer.相似文献
88.
J. Ch. Pomerol 《Mathematical Programming》1980,19(1):352-355
We give a new minisup theorem for noncompact strategy sets. Our result is of the type of the Matthies-Strang-Christiansen minimax theorem where the hyperplane should be replaced by any closed convex set. As an application, we derive a slight generalization of the Matthies-Strang-Christiansen minimax theorem. 相似文献
89.
R. S. Simon F. Folkmann Ch. Briançon J. Libert J. P. Thibaud R. J. Walen S. Frauendorf 《Zeitschrift für Physik A Hadrons and Nuclei》1980,298(2):121-128
In the actinides bothi 13/2 protons andj 15/2 neutrons are close to the Fermi surface. At rapid rotation these high-j particles will unpair and align their orbital angular momentum along the axis of rotation giving rise tos-bands that cross the ground-state band. Coulomb excitation of the odd nuclei 237 93 Np (established up to the 45/2+ state) and 235 92 U (established up to the 51/2? state) provides specific information about these band crossings: From the saturating alignment of the odd high-j particle in both nuclei at intermediate rotational frequencies we find the aligned angular momentum of thei 13/2 protons-band to be 6.6? while the corresponding value for thej 15/2 neutrons-band is 5.5?. At more rapid rotation above ?ω=0.18 MeV we observe additional alignment in235U. This is ascribed to the interaction of the protons-band. From the gradual onset of the additional alignment we deduce that forZ=92 the protons-band interacts strongly with the ground-state band and from a comparison of the actual amount of alignment with the full value of 6.6? we estimate the crossing to occur around ?gw c p =0.25 MeV. 相似文献
90.
H. R. Khan K. Lüders Ch. J. Raub G. Roth 《Zeitschrift für Physik B Condensed Matter》1980,38(1):27-33
Superconductivity, structure and electrical resistance behaviour of -phase alloys of Nb–Rh and Ta–Rh are investigated. The Ta–Rh alloys do not become superconducting above 1.2 K. The
andH
c2
(0) values of a homogeneous alloy with the composition Nb65.2Rh34.8 are 2.95 K, 13.9 kG/K and 23 kG, respectively, whereas for an inhomogeneous alloy with the composition Nb63.7Rh36.3 these values are 4.24 K, 5.5 kG/K and 14 kG, respectively. Splat quenching results in a substantial increase in the
andH
c2
(0) values of the Rh-rich sample. Annealing (900°C, 100 h) of the Rh-rich sample leads only to small changes in the superconducting properties but a small amount of Nb–Rh solid solution has been formed. The electrical resistance of Nb65.2Rh34.8 decreases with decreasing temperature and varies asT
0.5 between 150 and 240 K and asT between 60 and 140 K. For Ta70.0Rh30.0 the temperature coefficient changes to negative values below 170K. values are calculated for Nb–Rh using McMillan's formula. An estimatedT
c
value of Ta–Rh is 0.2 K. TheH
c2
(0) values of Nb–Rh are in good agreement with the theoreticalH
c
2**
(0) values.Dedicated to Prof. Dr. W. Buckel on the occasion of his 60th birthday 相似文献