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排序方式: 共有70条查询结果,搜索用时 46 毫秒
1.
H.O.U. Fynbo Y. Prezado J. Äystö U.C. Bergmann M.J.G. Borge P. Dendooven W. Huang J. Huikari H. Jeppesen P. Jones B. Jonson M. Meister G. Nyman M. Oinonen K. Riisager O. Tengblad I.S. Vogelius Y. Wang L. Weissman K.W. Rolander 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):135-138
2.
Antolín R Borge G Posada T Raposo JC Seara I Etxebarria N 《Journal of AOAC International》2004,87(5):1218-1223
A validation study was carried out in order to evaluate the efficiency of inductively coupled plasma-optical emission spectrometry (ICP-OES) for the analysis of minor elements (manganese, chromium, copper, iron, and titanium) in aluminium alloys. Aluminium casting samples were obtained by adding compressed powder compacts of each alloying element and aluminium (minitablets) to aluminum baths in a laboratory crucible furnace. Digestion of solid samples was performed using concentrated HCI and H202 35% (v/v) previous to analysis by ICP-OES without any matrix separation. This solution-based method was validated considering direct current arc spectrometry as the reference method based on direct analysis without any pretreatment of the solid samples considered. Univariate statistical procedures were carried out, for which precision <3% and trueness of the analytical results were taken into account. 相似文献
3.
Pablo Ríos Javier Borge Francisco Fernndez de Crdova Giuseppe Sciortino Agustí Lleds Amor Rodríguez 《Chemical science》2021,12(7):2540
The concept of metal–ligand cooperation opens new avenues for the design of catalytic systems that may offer alternative reactivity patterns to the existing ones. Investigations of this concept with ligands bearing a boron center in their skeleton established mechanistic pathways for the activation of small molecules in which the boron atom usually performs as an electrophile. Here, we show how this electrophilic behavior can be modified by the ligand trans to the boron center, evincing its ambiphilic nature. Treatment of diphosphinoboryl (PBP) nickel–methyl complex 1 with bis(catecholato)diboron (B2Cat2) allows for the synthesis of nickel(ii) bis-boryl complex 3 that promotes the clean and reversible heterolytic cleavage of dihydrogen leading to the formation of dihydroborate nickel complex 4. Density functional theory analysis of this reaction revealed that the heterolytic activation of H2 is facilitated by the cooperation of both boryl moieties and the metal atom in a concerted mechanism that involves a Ni(ii)/Ni(0)/Ni(ii) process. Contrary to 1, the boron atom from the PBP ligand in 3 behaves as a nucleophile, accepting a formally protic hydrogen, whereas the catecholboryl moiety acts as an electrophile, receiving the attack from the hydride-like fragment. This manifests the dramatic change in the electronic properties of a ligand by tuning the substituent trans to it and constitutes an unprecedented cooperative mechanism that involves two boryl ligands in the same molecule operating differently, one as a Lewis acid and the other one as a Lewis base, in cooperation with the metal. In addition, reactivity towards different nucleophiles such as amines or ammonia confirmed the electrophilic nature of the Bcat moiety, allowing the formation of aminoboranes.A bis(boryl)nickel complex promotes the facile and reversible activation of H2 through a cooperative mechanism that involves the metal and both boryl moieties in a concerted five-center process. 相似文献
4.
N. Etxebarria G. Arana R. Antolín G. Borge T. Posada J. C. Raposo 《Accreditation and quality assurance》2007,12(11):575-580
Electrolytic manganese is an important alloying element for aluminium and steel melts. It is mainly added to melts of aluminium
in the holding furnace as tablets or minitablets (compressed compacts of manganese and aluminium powders). Selenium derivates
are usually added during the production of electrolytic manganese, so some selenium is present in the alloys produced when
electrolytic manganese is added to the aluminium furnace. Since the selenium contents of many alloys are of concern from health
and environmental perspectives, their values should be provided. In this work, a laboratory reference material (LRM) based
on electrolytic manganese was produced to assure our routine quality control method, where selenium is analysed by hydride
generation followed by optical emission spectrometry with inductively coupled plasma (HG–ICP–OES). Therefore, the present
paper describes in detail the preparation procedure for and the results from homogeneity and stability studies performed on
electrolytic manganese LRM. For this purpose, a commercial electrolytic manganese lot was selected and the main factors involved
in the preparation of the material (pretreatment step, homogenization, bottling and storage) were carefully studied and established
in order to guarantee the long-term stability of the LRM. The results obtained showed that the LRM developed was a fit-for-purpose
material for the quality control of the routine analysis of selenium. 相似文献
5.
Ph Dessagne M. J. G. Borge J. Giovinazzo A. Huck A. Jokinen A. Knipper C. Longour G. Marguier M. Ramdhane V. Rauch O. Tengblad G. Walter Ch. Miehé 《The European Physical Journal A - Hadrons and Nuclei》2004,20(3):405-411
Challenged by recent theoretical work, a study of the
-EC decay of the N = Z even-even nucleus 76
Sr has been undertaken in order to assign the parent ground-state deformation. In this study 13 levels with
have been located in 76
Rb. The beta-delayed proton emission has been observed for the first time in an N = Z even-even nucleus. The
p branching ratio has been determined to be
. The 76
Sr half-life has been remeasured and a more precise value of
s has been obtained. On the basis of the comparison of measured Gamow-Teller strength with calculated strength distributions for both oblate and prolate deformation, it is concluded that the 76
Sr has strong prolate deformation in the ground state.Received: 26 June 2003, Revised: 5 November 2003, Published online: 18 June 2004PACS:
21.10.Hw Spin, parity, and isobaric spin - 23.20.Lv
transitions and level energies - 23.40.Hc Relation with nuclear matrix elements and nuclear structure - 27.50. + e
J. Giovinazzo: Present address: Centre d Etudes Nucléaires de Bordeaux-Gradignan, Le Haut Vigneau, F-33175 Gradignan Cedex, France.M. Ramdhane: Present address: University Mentouri, 25000 Constantine, Algeria. 相似文献
6.
Meister M Chulkov LV Simon H Aumann T Borge MJ Elze TW Emling H Geissel H Hellström M Jonson B Kratz JV Kulessa R Leifels Y Markenroth K Münzenberg G Nickel F Nilsson T Nyman G Pribora V Richter A Riisager K Scheidenberger C Schrieder G Tengblad O Zhukov MV 《Physical review letters》2003,91(16):162504
The one-proton knockout channel from 6He (240 MeV/u) impinging on a carbon target has been investigated. The triton fragments originating from this channel were detected in coincidence with the two neutrons. A broad structure, peaked at 3 MeV above the t+2n threshold, is observed in the t+n+n-relative energy spectrum. It is shown that this structure is mainly due to a I(pi)=1/2(+) resonance as expected for the 5H ground state, and from the observed angular and energy correlations, being used for the first time in 5H studies, that the neutrons to a large extent occupy the p shell. 相似文献
7.
8.
Labiche M Orr NA Marqués FM Angélique JC Axelsson L Benoit B Bergmann UC Borge MJ Catford WN Chappell SP Clarke NM Costa G Curtis N D'Arrigo A de Góes Brennand E Dorvaux O Fazio G Freer M Fulton BR Giardina G Grévy S Guillemaud-Mueller D Hanappe F Heusch B Jones KL Jonson B Le Brun C Leenhardt S Lewitowicz M Lopez MJ Markenroth K Mueller AC Nilsson T Ninane A Nyman G de Oliveira F Piqueras I Riisager K Saint Laurent MG Sarazin F Singer SM Sorlin O Stuttgé L 《Physical review letters》2001,86(4):600-603
The two-neutron halo nucleus (14)Be has been investigated in a kinematically complete measurement of the fragments ((12)Be and neutrons) produced in dissociation at 35 MeV/nucleon on C and Pb targets. Two-neutron removal cross sections, neutron angular distributions, and invariant mass spectra were measured, and the contributions from electromagnetic dissociation (EMD) were deduced. Comparison with three-body model calculations suggests that the halo wave function contains a large nu(2s(1/2))(2) admixture. The EMD invariant mass spectrum exhibited enhanced strength near threshold consistent with a nonresonant soft-dipole excitation. 相似文献
9.
R. Boutami M. J.G. Borge H. Mach L. M. Fraile K. Gulda A. J. Aas L. M. García-Raffi E. Hagebø W. Kurcewicz G. Løvhøiden T. Martínez B. Rubio J. L. Taín O. Tengblad 《The European physical journal. Special topics》2007,150(1):87-88
There is lack of knowledge of the structure of the 231Ac
nucleus located in the upper border of the
island of octupole deformation centered around A = 225.
We have populated the excited states in 231Ac by beta-decay from the parent 231Ra
produced at ISOLDE, CERN.
The low-energy structure of 231Ac has been investigated by
means of γ, conversion electrons, γ-γ and γ-e-
spectroscopy. We report here in the precise
determination in 231Ac of the half-life of the most intensively populated states
by the Advanced Time Delayed ββγ(t) technique. 相似文献