383 research outputs found
Lacustrine organic geochemistry--an overview of indicators of organic matter sources and diagenesis in lake sediments
The factors affecting the amounts and types of organic matter in lacustrine sediments are summarized in this review, and synthesis, of published studies. Biota living in the lake and in its watershed are the sources of the organic compounds initially contributed to the lake system. Microbial reworking of these materials during sinking and early sedimentation markedly diminishes the total amount of organic matter while replacing many of the primary compounds with secondary ones. Much of the organic matter content of sediments is the product of this microbial reprocessing. Various organic matter components of lake sediments nonetheless retain source information and thereby contribute to the paleolimnological record. Carbon/nitrogen ratios of total organic matter reflect original proportions of algal and land-derived material. Carbon isotopic compositions indicate the history of lake productivity and carbon recycling. Biomarker compounds provide important information about contributions from different biota. Sterol compositions and chainlength distributions of n-alkanes, n-alkanoic acids, and n-alkanols help distinguish different algal and watershed sources and also record diagenetic alterations.Stabilization of functional-group-containing biomarkers by conversion into saturated or aromatic hydrocarbons or by incorporation into bound forms improves their preservation and hence record of source information. Lignin components provide important evidence of watershed plant cover, and pigments reflect algal assemblages. The interplay of the factors influencing the organic matter content of lake sediments is illustrated by overviews of sedimentary records of four lake systems--Lake Biwa (Japan), Lake Greifen (Switzerland), Lake Washington (Pacific Northwest), and the Great Lakes (American Midwest).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30617/1/0000257.pd
Line shape of the muH(3p - 1s) hyperfine transitions
The (3p - 1s) X-ray transition to the muonic hydrogen ground state was
measured with a high resolution crystal spectrometer. A Doppler effect
broadening of the X-ray line was established which could be attributed to
different Coulomb de-excitation steps preceding the measured transition. The
assumption of a statistical population of the hyperfine levels of the muonic
hydrogen ground state was directly confirmed by the experiment and measured
values for the hyperfine splitting can be reported. The results allow a
decisive test of advanced cascade model calculations and establish a method to
extract fundamental strong-interaction parameters from pionic hydrogen
experiments.Comment: Submitted to Physical Review Letter
A New Measurement of Kaonic Hydrogen X rays
The system at threshold is a sensitive testing ground for low
energy QCD, especially for the explicit chiral symmetry breaking. Therefore, we
have measured the -series x rays of kaonic hydrogen atoms at the DANE
electron-positron collider of Laboratori Nazionali di Frascati, and have
determined the most precise values of the strong-interaction energy-level shift
and width of the atomic state. As x-ray detectors, we used large-area
silicon drift detectors having excellent energy and timing resolution, which
were developed especially for the SIDDHARTA experiment. The shift and width
were determined to be eV and
eV, respectively. The new
values will provide vital constraints on the theoretical description of the
low-energy interaction.Comment: 5 figures, submitted to Physics Letters
Beyond quantum mechanics? Hunting the 'impossible' atoms (Pauli Exclusion Principle violation and spontaneous collapse of the wave function at test)
The development of mathematically complete and consistent models solving the
so-called "measurement problem", strongly renewed the interest of the
scientific community for the foundations of quantum mechanics, among these the
Dynamical Reduction Models posses the unique characteristic to be
experimentally testable. In the first part of the paper an upper limit on the
reduction rate parameter of such models will be obtained, based on the analysis
of the X-ray spectrum emitted by an isolated slab of germanium and measured by
the IGEX experiment.
The second part of the paper is devoted to present the results of the VIP
(Violation of the Pauli exclusion principle) experiment and to describe its
recent upgrade. The VIP experiment established a limit on the probability that
the Pauli Exclusion Principle (PEP) is violated by electrons, using the very
clean method of searching for PEP forbidden atomic transitions in copper
Searches for the Violation of Pauli Exclusion Principle at LNGS in VIP(-2) experiment
The VIP (Violation of Pauli exclusion principle) experiment and its follow-up
experiment VIP-2 at the Laboratori Nazionali del Gran Sasso (LNGS) search for
X-rays from Cu atomic states that are prohibited by the Pauli Exclusion
Principle (PEP). The candidate events, if they exist, will originate from the
transition of a orbit electron to the ground state which is already
occupied by two electrons. The present limit on the probability for PEP
violation for electron is 4.7 set by the VIP experiment. With
upgraded detectors for high precision X-ray spectroscopy, the VIP-2 experiment
will improve the sensitivity by two orders of magnitude.Comment: 5 pages, 3 figures, 1 table. Conference proceedings for oral
presentation at TAUP 2015, Torin
High sensitivity tests of the Pauli Exclusion Principle with VIP2
The Pauli Exclusion Principle is one of the most fundamental rules of nature
and represents a pillar of modern physics. According to many observations the
Pauli Exclusion Principle must be extremely well fulfilled. Nevertheless,
numerous experimental investigations were performed to search for a small
violation of this principle. The VIP experiment at the Gran Sasso underground
laboratory searched for Pauli-forbidden X-ray transitions in copper atoms using
the Ramberg-Snow method and obtained the best limit so far. The follow-up
experiment VIP2 is designed to reach even higher sensitivity. It aims to
improve the limit by VIP by orders of magnitude. The experimental method,
comparison of different PEP tests based on different assumptions and the
developments for VIP2 are presented.Comment: 6 pages, 3 figures, Proceedings DISCRETE2014 Conferenc
Line shape analysis of the K transition in muonic hydrogen
The K transition in muonic hydrogen was measured with a
high-resolution crystal spectrometer. The spectrum is shown to be sensitive to
the ground-state hyperfine splitting, the corresponding triplet-to-singlet
ratio, and the kinetic energy distribution in the state. The hyperfine
splitting and triplet-to-singlet ratio are found to be consistent with the
values expected from theoretical and experimental investigations and,
therefore, were fixed accordingly in order to reduce the uncertainties in the
further reconstruction of the kinetic energy distribution. The presence of
high-energetic components was established and quantified in both a
phenomenological, i.e. cascade-model-free fit, and in a direct deconvolution of
the Doppler broadening based on the Bayesian approach.Comment: 22 pages, 21 figure
Testing the Pauli Exclusion Principle for electrons at LNGS
High-precision experiments have been done to test the Pauli exclusion
principle (PEP) for electrons by searching for anomalous -series X-rays from
a Cu target supplied with electric current. With the highest sensitivity, the
VIP (VIolation of Pauli Exclusion Principle) experiment set an upper limit at
the level of for the probability that an external electron captured
by a Cu atom can make the transition from the 2 state to a 1 state
already occupied by two electrons. In a follow-up experiment at Gran Sasso, we
aim to increase the sensitivity by two orders of magnitude. We show proofs that
the proposed improvement factor is realistic based on the results from recent
performance tests of the detectors we did at Laboratori Nazionali di Frascati
(LNF).Comment: 8 pages, 5 figures, conference proceedings on TAUP 201
Spontaneously emitted X-rays: an experimental signature of the dynamical reduction models
We present the idea of searching for X-rays as a signature of the mechanism
inducing the spontaneous collapse of the wave function. Such a signal is
predicted by the continuous spontaneous localization theories, which are
solving the "measurement problem" by modifying the Schrodinger equation. We
will show some encouraging preliminary results and discuss future plans and
strategy.Comment: to be published in Foundation of Physics 201
Application of photon detectors in the VIP2 experiment to test the Pauli Exclusion Principle
The Pauli Exclusion Principle (PEP) was introduced by the austrian physicist
Wolfgang Pauli in 1925. Since then, several experiments have checked its
validity. From 2006 until 2010, the VIP (VIolation of the Pauli Principle)
experiment took data at the LNGS underground laboratory to test the PEP. This
experiment looked for electronic 2p to 1s transitions in copper, where 2
electrons are in the 1s state before the transition happens. These transitions
violate the PEP. The lack of detection of X-ray photons coming from these
transitions resulted in a preliminary upper limit for the violation of the PEP
of . Currently, the successor experiment VIP2 is under
preparation. The main improvements are, on one side, the use of Silicon Drift
Detectors (SDDs) as X-ray photon detectors. On the other side an active
shielding is implemented, which consists of plastic scintillator bars read by
Silicon Photomultipliers (SiPMs). The employment of these detectors will
improve the upper limit for the violation of the PEP by around 2 orders of
magnitude
- …