3,937 research outputs found
Utilizing Colored Dissolved Organic Matter to Derive Dissolved Black Carbon Export by Arctic Rivers
Wildfires have produced black carbon (BC) since land plants emerged. Condensed aromatic compounds, a form of BC, have accumulated to become a major component of the soil carbon pool. Condensed aromatics leach from soils into rivers, where they are termed dissolved black carbon (DBC). The transport of DBC by rivers to the sea is a major term in the global carbon and BC cycles. To estimate Arctic river DBC export, 25 samples collected from the six largest Arctic rivers (Kolyma, Lena, Mackenzie, Obâ, Yenisey and Yukon) were analyzed for dissolved organic carbon (DOC), colored dissolved organic matter (CDOM), and DBC. A simple, linear regression between DOC and DBC indicated that DBC accounted for 8.9 Âą 0.3% DOC exported by Arctic rivers. To improve upon this estimate, an optical proxy for DBC was developed based upon the linear correlation between DBC concentrations and CDOM light absorption coefficients at 254 nm (a254). Relatively easy to measure a254 values were determined for 410 Arctic river samples between 2004 and 2010. Each of these a254 values was converted to a DBC concentration based upon the linear correlation, providing an extended record of DBC concentration. The extended DBC record was coupled with daily discharge data from the six rivers to estimate riverine DBC loads using the LOADEST modeling program. The six rivers studied cover 53% of the pan-Arctic watershed and exported 1.5 Âą 0.1 million tons of DBC per year. Scaling up to the full area of the pan-Arctic watershed, we estimate that Arctic rivers carry 2.8 Âą 0.3 million tons of DBC from land to the Arctic Ocean each year. This equates to ~8% of Arctic river DOC export, slightly less than indicated by the simpler DBC vs DOC correlation-based estimate. Riverine discharge is predicted to increase in a warmer Arctic. DBC export was positively correlated with river runoff, suggesting that the export of soil BC to the Arctic Ocean is likely to increase as the Arctic warms
Non-Destructive Identification of Cold and Extremely Localized Single Molecular Ions
A simple and non-destructive method for identification of a single molecular
ion sympathetically cooled by a single laser cooled atomic ion in a linear Paul
trap is demonstrated. The technique is based on a precise determination of the
molecular ion mass through a measurement of the eigenfrequency of a common
motional mode of the two ions. The demonstrated mass resolution is sufficiently
high that a particular molecular ion species can be distinguished from other
equally charged atomic or molecular ions having the same total number of
nucleons
Stability of atomic clocks based on entangled atoms
We analyze the effect of realistic noise sources for an atomic clock
consisting of a local oscillator that is actively locked to a spin-squeezed
(entangled) ensemble of atoms. We show that the use of entangled states can
lead to an improvement of the long-term stability of the clock when the
measurement is limited by decoherence associated with instability of the local
oscillator combined with fluctuations in the atomic ensemble's Bloch vector.
Atomic states with a moderate degree of entanglement yield the maximal clock
stability, resulting in an improvement that scales as compared to the
atomic shot noise level.Comment: 4 pages, 2 figures, revtex
Persuasive Technology for Learning and Teaching â The EuroPLOT Project
The concept of persuasive design has demonstrated its benefits by changing human behavior in certain situations, but in the area of education and learning, this approach has rarely been used. To change this and to study the feasibility of persuasive technology in teaching and learning, the EuroPLOT project (PLOT = Persuasive Learning Objects and Technologies) has been funded 2010-2013 by the Education, Audiovisual and Culture Executive Agency (EACEA) in the Life-long Learning (LLL) programme. In this program two tools have been developed (PLOTMaker and PLOTLearner) which allow to create learning objects with inherently persuasive concepts embedded. These tools and the learning objects have been evaluated in four case studies: language learning (Ancient Hebrew), museum learning (Kaj Munk Museum, Denmark), chemical handling, and academic Business Computing. These case studies cover a wide range of different learning styles and learning groups, and the results obtained through the evaluation of these case studies show the wide range of success of persuasive learning. They also indicate the limitations and areas where improvements are required
Demonstration of PLOTs from the EuroPLOT project
The EuroPLOT project (2010-2013) has been funded to explore the concept of persuasive design for learning and teaching. It has developed Persuasive Learn-ing Objects and Technologies (PLOTs), manifested in two tools and a set of learning objects that have been tested and evaluated in four different case studies. These PLOTs will be shown in this demonstration, and the participants can try them out and experience for themselves the impact of persuasive technology that is embedded in these PLOTs. This will be one authoring tool (PLOTMaker) and one delivery tool (PLOTLearner). Furthermore, there will be learning objects shown which have been developed for those four different case studies. All of these PLOTs have already been tested and evaluated during case studies with real learners
HANA: A HAndwritten NAme Database for Offline Handwritten Text Recognition
Methods for linking individuals across historical data sets, typically in
combination with AI based transcription models, are developing rapidly.
Probably the single most important identifier for linking is personal names.
However, personal names are prone to enumeration and transcription errors and
although modern linking methods are designed to handle such challenges these
sources of errors are critical and should be minimized. For this purpose,
improved transcription methods and large-scale databases are crucial
components. This paper describes and provides documentation for HANA, a newly
constructed large-scale database which consists of more than 1.1 million images
of handwritten word-groups. The database is a collection of personal names,
containing more than 105 thousand unique names with a total of more than 3.3
million examples. In addition, we present benchmark results for deep learning
models that automatically can transcribe the personal names from the scanned
documents. Focusing mainly on personal names, due to its vital role in linking,
we hope to foster more sophisticated, accurate, and robust models for
handwritten text recognition through making more challenging large-scale
databases publicly available. This paper describes the data source, the
collection process, and the image-processing procedures and methods that are
involved in extracting the handwritten personal names and handwritten text in
general from the forms
Distributed Quantum Computation Based-on Small Quantum Registers
We describe and analyze an efficient register-based hybrid quantum
computation scheme. Our scheme is based on probabilistic, heralded optical
connection among local five-qubit quantum registers. We assume high fidelity
local unitary operations within each register, but the error probability for
initialization, measurement, and entanglement generation can be very high
(~5%). We demonstrate that with a reasonable time overhead our scheme can
achieve deterministic non-local coupling gates between arbitrary two registers
with very high fidelity, limited only by the imperfections from the local
unitary operation. We estimate the clock cycle and the effective error
probability for implementation of quantum registers with ion-traps or
nitrogen-vacancy (NV) centers. Our new scheme capitalizes on a new efficient
two-level pumping scheme that in principle can create Bell pairs with
arbitrarily high fidelity. We introduce a Markov chain model to study the
stochastic process of entanglement pumping and map it to a deterministic
process. Finally we discuss requirements for achieving fault-tolerant operation
with our register-based hybrid scheme, and also present an alternative approach
to fault-tolerant preparation of GHZ states.Comment: 22 Pages, 23 Figures and 1 Table (updated references
Quantum simulations of the superfluid-insulator transition for two-dimensional, disordered, hard-core bosons
We introduce two novel quantum Monte Carlo methods and employ them to study
the superfluid-insulator transition in a two-dimensional system of hard-core
bosons. One of the methods is appropriate for zero temperature and is based
upon Green's function Monte Carlo; the other is a finite-temperature world-line
cluster algorithm. In each case we find that the dynamical exponent is
consistent with the theoretical prediction of by Fisher and co-workers.Comment: Revtex, 10 pages, 3 figures (postscript files attached at end,
separated by %%%%%% Fig # %%%%%, where # is 1-3). LA-UR-94-270
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