Chemical Weathering and Erosional Transport in an Ancient Shield Terrain

This project investigates how isotope systems respond to changes in continental weathering processes and the consequences for the chemical composition of the oceans. Both experimental and natural data indicate that Li and Mg stable isotope systems preserve information on the mineral reactions controlling water chemistry. Dissolution experiments indicate that primary mineral dissolution has little effect on Li, but does fractionate the isotopes of Mg, whereas secondary mineral formation involves preferential uptake of the lighter isotopes of both Li and Mg. Glacial regions have low chemical weathering rates so their rivers should, in principal, have Li isotope compositions (δ7Li) that are similar to those of the underlying rock. In practise, glacial rivers in Greenland have δ7Li values that differ significantly from the source rock. Subglacial uptake of 6Li by iron oxyhydroxides appears to influence the riverine Li isotope composition. In contrast, the principal control on Mg isotopes in glacial rivers appears to be primary mineral weathering. Carbonate dissolution dominates the chemistry of glacial rivers, and this phase possesses a light Mg isotope composition imparting this signature to the Greenland rivers. Both the Li and Mg isotope compositions of glacial rivers are similar to their respective global riverine averages, suggesting that the impact of glaciation on the Li and Mg composition of seawater may be small. The Re-Os radiogenic isotope system is also a useful tracer of continental weathering, its composition in the oceans being sensitive to changes in the flux and composition of continental weathering. Laterites are widespread in tropical regions and are shown to contain high concentrations of highly unradiogenic Os. Consequently, their subsequent weathering and erosion has potential to significantly affect the Os isotope composition delivered to the oceans

Mg isotopic heterogeneity, Al-Mg isochrons, and canonical ^(26)Al/^(27)Al in the early solar system

There is variability in the Mg isotopic composition that is a reflection of the widespread heterogeneity in the isotopic composition of the elements in the solar system at approximately 100 ppm. Measurements on a single calcium-aluminum-rich inclusion (CAI) gave a good correlation of ^(26)Mg/^(24)Mg with ^(27)Al/^(24)Mg, yielding an isochron corresponding to an initial (^(26)Al/^(27)Al)_o = (5.27 ± 0.18) × 10^(−5) and an initial (^(26)Mg/^(24)Mg)_o = −0.127 ± 0.032‰ relative to the standard. This isochron is parallel to that obtained by Jacobsen et al. (2008), but is distinctively offset. This demonstrates that there are different initial Mg isotopic compositions in different samples with the same ^(26)Al/^(27)Al. No inference about uniformity/heterogeneity of ^(26)Al/^(27)Al on a macro scale can be based on the initial (^(26)Mg/^(24)Mg)_o values. Different values of ^(26)Al/^(27)Al for samples representing the same point in time would prove heterogeneity of ^(26)Al/^(27)Al. The important issue is whether the bulk solar inventory of ^(26)Al/^(27)Al was approximately 5 × 10^(−5) at some point in the early solar system. We discuss ultra refractory phases of solar type oxygen isotope composition with ^(26)Al/^(27)Al from approximately 5 × 10^(−5) to below 0.2 × 10^(−5). We argue that the real issues are: intrinsic heterogeneity in the parent cloud; mechanism and timing for the later production of ^(16)O-poor material; and the relationship to earlier formed ^(16)O-rich material in the disk. ^(26)Al-free refractories can be produced at a later time by late infall, if there is an adequate heat source, or from original heterogeneities in the placental molecular cloud from which the solar system formed

Fall, Recovery and Characterization of the Novato L6 Chondrite Breccia

The Novato L6 chondrite fragmental breccia fell in California on 17 October 2012, and was recovered after the Cameras for Allsky Meteor Surveillance (CAMS) project determined the meteor's trajectory between 95 and 45 km altitude. The final fragmentation at 33 1 km altitude was exceptionally well documented by digital photographs. The first sample was recovered before rain hit the area. First results from a consortium study of the meteorite's characterization, cosmogenic and radiogenic nuclides, origin and conditions of the fall are presented. Some meteorites did not retain fusion crust and show evidence of spallation. Before entry, the meteoroid was 35+/-5 cm in diameter (mass 80+/-35 kg) with a cosmic ray exposure age of 9+/-1 Ma, if it had a one-stage exposure history. However, based on the cosmogenic nuclide inventory, a two-stage exposure history is more likely, with lower shielding in the last few Ma. Thermoluminescence data suggest a collision event within the last approx. 0.1 Ma. Novato likely belonged to the class of shocked L chondrites that have a common shock age of 470 Ma, based on the U,Th-He age of 460+/-220 Ma. The measured orbits of Novato, Jesenice and Innisfree are consistent with a proposed origin of these shocked L chondrites in the Gefion asteroid family, but leave open the possibility that they came to us directly from the 5:2 mean motion resonance with Jupiter. Novato experienced a stronger compaction than did other L6 chondrites of shock-stage S4. Despite this, a freshly broken surface shows a wide range of organic compounds

Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis

Search for heavy resonances decaying to two Higgs bosons in final states containing four b quarks

A search is presented for narrow heavy resonances X decaying into pairs of Higgs bosons (H) in proton-proton collisions collected by the CMS experiment at the LHC at root s = 8 TeV. The data correspond to an integrated luminosity of 19.7 fb(-1). The search considers HH resonances with masses between 1 and 3 TeV, having final states of two b quark pairs. Each Higgs boson is produced with large momentum, and the hadronization products of the pair of b quarks can usually be reconstructed as single large jets. The background from multijet and t (t) over bar events is significantly reduced by applying requirements related to the flavor of the jet, its mass, and its substructure. The signal would be identified as a peak on top of the dijet invariant mass spectrum of the remaining background events. No evidence is observed for such a signal. Upper limits obtained at 95 confidence level for the product of the production cross section and branching fraction sigma(gg -> X) B(X -> HH -> b (b) over barb (b) over bar) range from 10 to 1.5 fb for the mass of X from 1.15 to 2.0 TeV, significantly extending previous searches. For a warped extra dimension theory with amass scale Lambda(R) = 1 TeV, the data exclude radion scalar masses between 1.15 and 1.55 TeV

Search for supersymmetry in events with one lepton and multiple jets in proton-proton collisions at root s=13 TeV

Peer reviewe

Measurement of the top quark mass using charged particles in pp collisions at root s=8 TeV

Peer reviewe

Search for anomalous couplings in boosted WW/WZ -> l nu q(q)over-bar production in proton-proton collisions at root s=8TeV

Peer reviewe

Precise determination of the lutetium isotopic composition in rocks and minerals using multicollector ICPMS

Evidence of 176Hf excess in select meteorites older than 4556Ma was suggested to be caused by excitation of long-lived natural radionuclide 176Lu to its short-lived isomer 176mLu, due to an irradiation event during accretion in the early solar system. A