Distribution coefficients of Kd (REE: ppt./sol.) with REE = lanthanides (Ln), Y, and Sc between Fe Mn oxyhydroxide precipitates and NaCI solutions have been determined in pH = 5.4-6.4 at room tempera ture and atmospheric pressure. The logKd(Ln) values show convex tetrad effect variations across the series and positive Ce anomalies. Kd(Y) values are significantly lower than those for Ho and Er, whereas Kd(Sc) values are higher than those for Lu. Behaviors of Y3+ and.Sc3+ are distinct from heavy Ln3+ when REE coprecipitate with Fe-Mn oxyhydroxides in weakly acid solutions. The observed convex tetrad effect variations of logKd(Ln) are commonly modified from theoretically expected ones in light Ln and heavier Ln. The variations of logKd(Ln) across the series are related to { AG°f(Ln3+, aq) OG°f(Ln(OH)3.nH2O) } for the following reactions between Ln3+(aq) and Ln(OH)3.nH2O as precipitate: Ln(OH)3.nH2O(ss) + 3H+(aq) = Ln3+(aq) + (3 + n)H20(l). Hence, the variations of logKd(Ln) reflect (i) the tetrad effect origi nating from differences in Racah E1 and E3 parameters for 4f electron repulsion in Ln3+ ions between the two Ln(III) series, and (ii) the changes of coordination states of Ln3+ ions in the respective Ln(III) com plex series. The structural changes of the first-coordination spheres of Ln3+ ions in light Ln3+(aq) and heavy Ln(OH)3.nH2O series make the series variation of logKd(Ln) irregular. When we correct the logKd(Ln) values for the structural changes, they become regular tetrad effect variations compatible with the refined spin-pairing energy theory. Racah parameters for 4f electron repulsion in Ln3+ ions of octahydrate Ln3+(aq) series are inferred to be larger than those of Ln(OH)3.nH2O.

Chemical characteristics of "diagenetic" and "hydrogenous" type deep-sea nodules from the central and northeastern Pacific were studied regarding their Ce anomalies and Y fractionation from heavy REE. Pacific nodules of both types show low Y/Ho ratios less than average shales or chondrites, contrasting to the other marine samples (seawaters, limestones, and phosphorites) having higher Y/Ho ratios than aver age shales or chondrites. The "hydrogenous" type nodules show large positive Ce anomalies up to log(Ce/ Ce*) = +0.6, whereas the "diagenetic" type nodules display only small positive Ce anomalies or even small negative ones. Two nodule subsamples, which are characterized by 10 A manganate but are chemi cally the intermediate between the two types, show Ce anomalies of log(Ce/Ce*) = +0.3 in the middle of the two end members. Interestingly, the Ce anomalies of the nodules vary coherently with their logarith mic Co/(Ni+Cu) ratios. This positive correlation is valid even after combing many literature data of Pa cific nodules with our data. In the plot of Ce anomaly vs. log[Co/(Ni+Cu)], the three distinct types of Pacific nodules are systematically distinguished: "sub oxic-diagenetis" <_ "diagenetic" <_ "hydrogenous". The systematics strongly suggest that: (i) the Ce anomaly and log[Co/(Ni+Cu)] are similar geochemical indexes showing how effectively oxidative uptake of Ce and Co occurred in each nodule relative to non oxidative uptake of nutrient-type metals in the respective metal groups, and (ii) there exists an initial source supplying metals common to all the types of Pacific nodules. We inferred from various reasons that the common initial source is biogenic particulates delivered from overlying surface water. Oxidative up take of Ce and Co by fast sinking large biogenic particulates is less effective, but such particulates can more effectively convey nutrient-type metals involved with them to the sea floor because of their shorter residence time in oxic water. However, the relationship between metal transports of scavenged and nutri ent-type elements is reversed in the case of slowly sinking biogenic particulates. High surface productiv ity inevitably provides high flux of fast sinking large organic particulates, whereas low productivity gives rise to organic particulate flux dominated by slowly sinking small ones. These mechanisms explain the observed systematics of Ce anomaly vs. log[Co/(Ni+Cu)] plots for Pacific nodules.

We have investigated the thermal degradation of spin valve multilayers caused by annealing at 250-300°C, and determined that it significantly depended on selection of antiferromagnetic layers. Spin valves with a CuAu-I type ordered PtMn antiferromagnetic layer exhibited better thermal stability than those with a disordered Rh 17 -Mn 83 or an Ir 20 -Mn 80 layer. Comparing the magnetoresistance ratio dR/R of those spin valves after annealing at 280°C for 5 h, that of PtMn spin valves was more than 60% higher than the others, even though the same stack of layers was used, except the antiferromagnetic layer. Such an excellent thermal stability of PtMn spin valves was attributed to less Mn migration over the existing layers after annealing. This indicated that Mn impurities in ferromagnetic layers such as Co 90 -Fe 10 or Ni 81 -Fe 19 deleteriously affected the spin-dependent scattering of conduction electrons.

No abstract

The radical copolymerization of alkyl 2-norbornene-2-carboxylates, 1a-c, with alkyl (meth)acrylates, to produce copolymers with norbornane in the main chain, is described here. g-Butyrolactone-and hydroxy group-containing norbornene-based monomers (1b and 1c, respectively) were freshly synthesized, and their radical copolymerization behavior with n-butyl acrylate was examined. Methyl 2-norbornene-2-carboxylate, 1a, and the new monomers, 1b and 1c, were employed as comonomers for radical terpolymerization with lactone-and adamantane-containing (meth)acrylates to produce copolymers that could be applied as new, more chemically robust 193-nm photoresist materials. The dissolution rate of the spin-coated copolymer films after exposure to a photoacid generator, a significant characteristic in the photoresist application, was measured for various exposure doses of 193-nm ArF laser light under standard conditions in an aqueous alkaline solution.