U–Th–Pb isotopic systems have been studied in submillimeter-thick outermost layers of Quaternary opal occurring in calcite–silica fracture and cavity coatings within Tertiary tuffs at Yucca Mountain, Nevada, USA. These coatings preserve a record of paleohydrologic conditions at this site, which is being evaluated as a potential high-level nuclear waste repository. The opal precipitated from gro...

We investigate the relative influence of mantle upwelling velocity and source heterogeneity on the melting rates recorded by Th–U, Pa–U and Ra–Th disequilibria in post-glacial tholeiites from Iceland’s main rift areas. The measured (Th/U) ratios range from 1.085 to 1.247, the (Pa/U) ratios from 1.333 to 1.925, and the (Ra/Th) ratios from 0.801 to 1.218. A general positive correlation between Th...

neyshabour turquoise mine is located in northwest of neyshabour, southern quchan volcanic belt. eocene andesite and dacite forming as lava and pyroclastic rocks cover most of the area. subvolcanic diorite to syenite porphyry (granitoids of magnetite series) intruded the volcanic rocks. both volcanic and subvolcanic rocks are highly altered. four types of alteration are recognized including: sil...

S c h o o l o f In fo rm a tio n S c ie n c e s a n d T e c h n o lo g y 0 0 4 D T h o m a s B u ild in g T h e P e n n s y lv a n ia S ta te U n iv e rs ity U n iv e rs ity P a rk , P A 1 6 8 0 2 , U S A jy e n @ is t.p s u .e d u Ab s tr a c t H o w a g e n ts a c c o m p lis h a g o a l ta s k in a m u lti-a g e n t s y s te m is u s u a lly s p e c ifie d b y m u lti-a g e n t p la n s b u ...

In tro d u c tio n It is ju s t o v er six a n d a h a lf d ecad es ago tiia t th e f irs t q u ah fied s is te r tu to r (now d esig n a ted n u rse tu to r ) w as a p p o in te d in th is c o u n try . S o u th A fr ic a ’s f irs t siste r tu to r , a single y o u n g fem ale , w as recru ited fro m E n g lan d an d held th e d is tin c tio n o f b e ing a g o ld m ed a lis t o f th e N ig h ...

Tim o th y H ig h le y , P a u l F. R e y n o ld s U n iv e rs ity o f V irg in ia { tjh ig h le y , re y n o ld s } @ v irg in ia .e d u V iv e k a n a n d V e lla n k i IB M , R e s e a rc h Tria n g le P a rk v e lla n k i@ u s .ib m .c o m Ab s tr a c t C o s t-b e n e fit a n a ly s is a tte m p ts to b a la n c e th e b e n e fits o f file p re fe tc h in g a g a in s t th e c o s ts o f ...