3,318 research outputs found
Tourmaline Composition of the Kı¸sladag Porphyry Au Deposit,Western Turkey: Implication of Epithermal Overprint
The Kışladağ porphyry Au deposit occurs in a middle Miocene magmatic complex comprising three different intrusions and magmatic-hydrothermal brecciation related to the multiphase effects of the different intrusions. Tourmaline occurrences are common throughout the deposit, mostly as an outer alteration rim around the veins with lesser amounts disseminated in the intrusions, and are associated with every phase of mineralization. Tourmaline mineralization has developed as a tourmaline-rich matrix in brecciated zones and tourmaline-quartz and/or tourmaline-sulfide veinlets within the different intrusive rocks. Tourmaline was identified in the tourmaline-bearing breccia zone (TBZ) and intrusive rocks that had undergone potassic, phyllic, and advanced argillic alteration. The tourmaline is present as two morphological varieties, aggregates of fine crystals (rosettes, fan-shaped) and larger isolated crystals and their aggregates. Four tourmaline generations (tourmaline I to IV) have different compositions and substitutions. Tourmaline I in TBZ and INT#1 is distinguished by the highest Fetot and enriched in Fe3+. Tourmalines II and III occur as fine aggregates, accompanied by the formation of isolated crystals and are characterized by lower Fetot and Fe3+. Tourmaline IV is characterized by the lowest Fetot, enriched in Cl, and has the highest proportion of X-site vacancy among all the tourmalines. Tourmaline I may be attributed to the potassic stage in INT#1 and early tourmaline in TBZ. Tourmalines II and III from INT#1 and the TBZ could be referred to the phyllic stage. The low Fe content in tourmaline is caused by the simultaneous deposition of sulfide minerals. Tourmaline IV from the TBZ and tourmaline II from INT#3 are distinguished by the high X-site vacancy proportion up to the formation of X-site vacant species as well as enriched in Cl; they can be attributed to the argillic stage of the hydrothermal process. The textural and especially chemical data of the tourmaline from the Kışladağ Au deposit provide information on the physico-chemical conditions during the porphyry to epithermal transition and subsequent epithermal overprinting
Thermal effects versus spin nematicity in a frustrated spin-1/2 chain
The spin-nematic phase is an intriguing state of matter that lacks usual
long-range dipolar order, yet it exhibits higher multipolar order. This makes
its detection extremely difficult and controversial. Recently, nuclear magnetic
resonance (NMR) has been proposed as one of the most suitable techniques to
confirm its existence. We report a O NMR observation of the reduction of
the local magnetization in the polarized state of the frustrated spin-1/2 chain
-TeVO, which was previously proposed to be a fingerprint of the
spin-nematic behavior. However, our detailed study shows that the detected
missing fraction of the magnetization, probed by NMR frequency shift, is
thermally activated, thus undermining the presence of the spin-nematic phase in
the investigated compound. This highlights the importance of careful
considerations of temperature-dependent NMR shift that has been overlooked in
previous studies of spin nematicity.Comment: accepted for publication in PRB(R), with supplementar
Efficiency determination of resistive plate chambers for fast quasi-monoenergetic neutrons
Composite detectors made of stainless steel converters and multigap resistive
plate chambers have been irradiated with quasi-monoenergetic neutrons with a
peak energy of 175MeV. The neutron detection efficiency has been determined
using two different methods. The data are in agreement with the output of Monte
Carlo simulations. The simulations are then extended to study the response of a
hypothetical array made of these detectors to energetic neutrons from a
radioactive ion beam experiment.Comment: Submitted to Eur.Phys.J. A; upgraded version correcting some typos
and updating ref.
New high magnetic field phase of the frustrated chain compound LiCuVO
Magnetization of the frustrated chain compound LiCuVO, focusing
on high magnetic field phases, is reported. Besides a spin-flop transition and
the transition from a planar spiral to a spin modulated structure observed
recently, an additional transition was observed just below the saturation
field. This newly observed magnetic phase is considered as a spin nematic
phase, which was predicted theoretically but was not observed experimentally.
The critical fields of this phase and its dM/dH curve are in good agreement
with calculations performed in a microscopic model (M. E. Zhitomirsky and H.
Tsunetsugu, preprint, arXiv:1003.4096v2).Comment: 5 pages, 4 figure
Mechanism of Pion Production in p Scattering at 1 GeV/nucleon
The one-pion and two-pion production in the p(alpha, alpha prime)X reaction
at an energy of E{alpha} = 4.2 GeV has been studied by simultaneous
registration of the scattered alpha particles and the secondary pion or proton.
The obtained results demonstrate that the inelastic alpha-particle scattering
on the proton at the energy of the experiment proceeds either through
excitation and decay of Delta resonance in the projectile or through excitation
in the target proton of the Roper resonance, which decays mainly on a nucleon
and a pion or a nucleon and a sigma meson - system of two pions in the isospin
I = 0, S-wave.Comment: 16 pages, 10 figures. Submitted to Proceedings of the XX
International Baldin Seminar on High - Energy Physics Problems, Dubna,
October 4 - 9, 201
Dynamics of a Simple Quantum System in a Complex Environment
We present a theory for the dynamical evolution of a quantum system coupled
to a complex many-body intrinsic system/environment. By modelling the intrinsic
many-body system with parametric random matrices, we study the types of
effective stochastic models which emerge from random matrix theory. Using the
Feynman-Vernon path integral formalism, we derive the influence functional and
obtain either analytical or numerical solutions for the time evolution of the
entire quantum system. We discuss thoroughly the structure of the solutions for
some representative cases and make connections to well known limiting results,
particularly to Brownian motion, Kramers classical limit and the
Caldeira-Leggett approach.Comment: 41 pages and 12 figures in revte
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