53 research outputs found
A new Holocene record of geomagnetic secular variation from Windermere, UK
Paleomagnetic
secular
variation
(PSV)
records
serve
as
valuable
independent
stratigraphic
correlation
and
dating
tools
for
marine
and
terrestrial
sediment
sequences,
and
enhance
knowledge
of
geomagnetic
field
dynamics.
We
present
a
new
radiocarbon-dated
record
(WINPSV-12K)
of
Holocene
geomagnetic
secular
variation
from
Windermere,
updating
the
existing
1981
UK
master
PSV
curve.
Our
analyses
used
continuous
U-channel
samples
taken
from
the
center
of
four
sediment
cores
retrieved
from
Windermere
in
2012.
The
natural
remanent
magnetization
(NRM)
of
each
U-channel
was
measured
before
and
after
stepwise
alternating
field
(AF)
demagnetization
on
a
superconducting
rock
magnetometer
at
intervals
of
0.5-cm
or
1-cm.
The
NRM
data
reveal
a
stable
and
well-defined
primary
magnetization.
Component
declinations
and
inclinations
estimated
using
Principal
Component
Analysis
(PCA)
of
NRM
data
from
the
four
Windermere
cores
correlate
well
on
their
independent
radiocarbon
age
models.
The
four
records
were
stacked
using
a
sliding
window
bootstrap
method,
resulting
in
a
composite
Holocene
PSV
record
(WINPSV-12K).
On
millennial
timescales
WINPSV-12K
correlates
well
with
other
records
from
Western
Europe
and
the
northern
North
Atlantic
to
a
resolution
of
∼
1
kyr,
given
age
uncertainties
and
spatial
variability
between
records.
WINPSV-12K
also
compares
well
to
the
CALS10k.2
and
pfm9k.1a
model
predictions
for
Windermere.
Key
regionally-significant
PSV
inclination
features
of
WINPSV-12K
which
correlate
with
other
North
Atlantic
records
include
peaks
at
5–6,
8.5,
and
10 cal ka BP,
and
a
trough
at
7calkaBP.
Key
PSV
declination
features
include
the
eastward
swing
from
5.5–2.3 cal ka BP
followed
by
a
major
westward
excursion
at
2.3 cal ka BP,
peaks
at
1.1
and
7calkaBP,
and
troughs
at
5.4
and
8.2 cal ka BP,
with
the
caveat
that
an
estimated
magnetic
lock-in
delay
of
at
least
100–200 yr
is
present.
PSV
variations
on
1–3 kyr
timescales
are
interpreted
to
represent
strengthening
and
weakening
of
the
North
American
versus
the
Siberian
and
European–Mediterranean
high-latitude
flux
lobes,
based
on
the
close
similarities
between
the
North
Atlantic
regional
records
and
the
antiphase
existing
in
the
East
Asian
Stack
record
and
the
North
East
Pacific
inclination
stack.
WINPSV-12K
provides
a
regionally-important
new
PSV
reference
curve
whose
prominent
features
may
serve
as
stratigraphic
markers
for
North
Atlantic
paleo-records
Decoherence in trapped ions due to polarization of the residual background gas
We investigate the mechanism of damping and heating of trapped ions
associated with the polarization of the residual background gas induced by the
oscillating ions themselves. Reasoning by analogy with the physics of surface
electrons in liquid helium, we demonstrate that the decay of Rabi oscillations
observed in experiments on 9Be+ can be attributed to the polarization phenomena
investigated here. The measured sensitivity of the damping of Rabi oscillations
with respect to the vibrational quantum number of a trapped ion is also
predicted in our polarization model.Comment: 26 pdf pages with 5 figures, http://www.df.ufscar.br/~quantum
Cost effectiveness of a 1-hour high-sensitivity troponin-T protocol: an analysis of the RAPID-TnT trial
Background: To understand the economic impact of an accelerated 0/1-hour high-sensitivity troponin-T (hs-cTnT) protocol. Objective:
To conduct a patient-level economic analysis of the RAPID-TnT randomised trial in patients presenting with suspected acute coronary syndrome (ACS). Methods: An economic evaluation was conducted with 3265 patients randomised to either the 0/1-hour hs-cTnT protocol (n = 1634) or the conventional 0/3-hour standard-of-care protocol (n = 1631) with costs reported in Australian dollars. The primary clinical outcome was all-cause mortality or new/recurrent myocardial infarction. Results:
Over 12-months, mean per patient costs were numerically higher in the 0/1-hour arm compared to the conventional 0/3-hour arm (by -1,380.15 to 891.22/patient, 95 %CI: 152.44/patient, 95 %CI:2,097.99, P = 0.988), whilst the reduction in ED LOS was more pronounced (by 0.70 h/patient, 95 %CI: 0.45–0.95, P < 0.001). Conclusions: There were no differences in resource utilization between the 0/1-hour hs-cTnT protocol versus the conventional 0/3-hour protocol for the assessment of suspected ACS, despite improved initial ED efficiency. Further refinements in strategies to improve clinical outcomes and subsequent management efficiency are needed.Ming-yu Anthony Chuang Emmanuel S. Gnanamanickam, Jonathan Karnon,
Kristina Lambrakis, Matthew Horsfall, Andrew Blyth ... et al
Protons in near earth orbit
The proton spectrum in the kinetic energy range 0.1 to 200 GeV was measured
by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at
an altitude of 380 km. Above the geomagnetic cutoff the observed spectrum is
parameterized by a power law. Below the geomagnetic cutoff a substantial second
spectrum was observed concentrated at equatorial latitudes with a flux ~ 70
m^-2 sec^-1 sr^-1. Most of these second spectrum protons follow a complicated
trajectory and originate from a restricted geographic region.Comment: 19 pages, Latex, 7 .eps figure
A Study of Cosmic Ray Secondaries Induced by the Mir Space Station Using AMS-01
The Alpha Magnetic Spectrometer (AMS-02) is a high energy particle physics
experiment that will study cosmic rays in the to range and will be installed on the International Space Station
(ISS) for at least 3 years. A first version of AMS-02, AMS-01, flew aboard the
space shuttle \emph{Discovery} from June 2 to June 12, 1998, and collected
cosmic ray triggers. Part of the \emph{Mir} space station was within the
AMS-01 field of view during the four day \emph{Mir} docking phase of this
flight. We have reconstructed an image of this part of the \emph{Mir} space
station using secondary and emissions from primary cosmic rays
interacting with \emph{Mir}. This is the first time this reconstruction was
performed in AMS-01, and it is important for understanding potential
backgrounds during the 3 year AMS-02 mission.Comment: To be submitted to NIM B Added material requested by referee. Minor
stylistic and grammer change
Perturbative Approach to Higher Derivative Theories with Fermions
We extend the perturbative approach developed in an earlier work to deal with
Lagrangians which have arbitrary higher order time derivative terms for both
bosons and fermions. This approach enables us to find an effective Lagrangian
with only first time derivatives order by order in the coupling constant. As in
the pure bosonic case, to the first order, the quantized Hamiltonian is bounded
from below whenever the potential is. We show in the example of a single
complex fermion that higher derivative interactions result in an effective mass
and change of vacuum for the low energy modes. The supersymmetric
noncommutative Wess-Zumino model is considered as another example. We also
comment on the higher derivative terms in Witten's string field theory and the
effectiveness of level truncation.Comment: Latex, 21 pages, minor modification, ref. adde
Large expert-curated database for benchmarking document similarity detection in biomedical literature search
Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe
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