11,767 research outputs found
Integrated stratigraphy of the Waitakian-Otaian Stage boundary stratotype, Early Miocene, New Zealand
The base of the type section of the Otaian Stage at Bluecliffs, South Canterbury, is recognised as the stratotype for the boundary between the Waitakian and Otaian Stages. Principal problems with the boundary are the restriction of existing bioevent proxies to shelf and upper slope environments and its uncertain age. These topics are addressed by a multidisplinary study of a 125 m section about the boundary, which examines its lithostratigraphy, depositional setting, biostratigraphy, correlation, and geochronology.
The lower siltstone lithofacies (0-38.5 m) was deposited at upper bathyal depths (200-600 m) in a marginal basin which was partially sheltered from fully oceanic circulation by a submarine high and islands. The site was covered by cool-temperate water and was probably adjacent to the Subtropical Convergence. This unit is succeeded by the banded lithofacies (38.5-106 m) and the upper siltstone lithofacies (basal 19 m studied). Paleodepth probably declined up-sequence, but deposition at shelf depths is not definitely indicated. A cyclic pattern of abundance spikes in benthic and planktonic foraminifera commences 9 m above base and extends to 73 m in the banded lithofacies. Oxygen isotope excursions (up to 2.08%) in Euuvigerina miozea and Cibicides novozelandicus are greatest within the interval containing the abundance spikes. The stage boundary occurs in the banded lithofacies at the highest abundance spike (73 m). Although condensed intervals might affect the completeness of the section, they are not associated with sedimentary discontinuities, and we consider that the section is suitable as a biostratigraphic reference.
Spores, pollens, dinoflagellates, calcareous nannofossils, foraminifera, bryozoans, and ostracods are preserved near the boundary, but molluscs principally occur higher, in the shallower upper siltstone lithofacies. Siliceous microfossils are rare. There is considerable scope for further biostratigraphic research.
The primary event marking the boundary at 73 m is the appearance of the benthic foraminifer Ehrenbergina marwicki. This is a distinctive and widely distributed event but is restricted to shelf and upper bathyal environments. Supplementary events in planktonic foraminifera and calcareous nannofossils were researched. Highest occurrences of Globigerina brazieri and G. euapertura are recorded at 47 and 58 m. There is a marked decline in relative abundance of Paragloborotalia spp. at 62 m. Helicosphaera carteri becomes more abundant than H. euphratis between 56 and 87 m. These events are not exact proxies for the boundary but they may usefully indicate proximity to it. They occur in the interval of prominent spikes in foraminiferal abundance.
The Waitakian-Otaian boundary is dated at 21.7 Ma by strontium isotopes. Stable primary remanence could not be determined in a pilot paleomagnetic study of Bluecliffs specimens. However, specimens trended towards reversed polarity, and remagnetisation great circle analysis will allow directions to be calculated in future collections
Linear Collider Capabilities for Supersymmetry in Dark Matter Allowed Regions of the mSUGRA Model
Recent comparisons of minimal supergravity (mSUGRA) model predictions with
WMAP measurements of the neutralino relic density point to preferred regions of
model parameter space. We investigate the reach of linear colliders (LC) with
and 1 TeV for SUSY in the framework of the mSUGRA model. We find
that LCs can cover the entire stau co-annihilation region provided \tan\beta
\alt 30. In the hyperbolic branch/focus point (HB/FP) region of parameter
space, specialized cuts are suggested to increase the reach in this important
``dark matter allowed'' area. In the case of the HB/FP region, the reach of a
LC extends well past the reach of the CERN LHC. We examine a case study in the
HB/FP region, and show that the MSSM parameters and can be
sufficiently well-measured to demonstrate that one would indeed be in the HB/FP
region, where the lightest chargino and neutralino have a substantial higgsino
component.Comment: 29 pages, 15 EPS figures; updated version slightly modified to
conform with published versio
Scaling and Formulary cross sections for ion-atom impact ionization
The values of ion-atom ionization cross sections are frequently needed for
many applications that utilize the propagation of fast ions through matter.
When experimental data and theoretical calculations are not available,
approximate formulas are frequently used. This paper briefly summarizes the
most important theoretical results and approaches to cross section calculations
in order to place the discussion in historical perspective and offer a concise
introduction to the topic. Based on experimental data and theoretical
predictions, a new fit for ionization cross sections is proposed. The range of
validity and accuracy of several frequently used approximations (classical
trajectory, the Born approximation, and so forth) are discussed using, as
examples, the ionization cross sections of hydrogen and helium atoms by various
fully stripped ions.Comment: 46 pages, 8 figure
Spectroscopic variability of two Oe stars
The Oe stars HD45314 and HD60848 have recently been found to exhibit very
different X-ray properties: whilst HD60848 has an X-ray spectrum and emission
level typical of most OB stars, HD45314 features a much harder and brighter
X-ray emission, making it a so-called gamma Cas analogue. Monitoring the
optical spectra could provide hints towards the origin of these very different
behaviours. We analyse a large set of spectroscopic observations of HD45314 and
HD60848, extending over 20 years. We further attempt to fit the H-alpha line
profiles of both stars with a simple model of emission line formation in a
Keplerian disk. Strong variations in the strengths of the H-alpha, H-beta, and
He I 5876 emission lines are observed for both stars. In the case of HD60848,
we find a time lag between the variations in the equivalent widths of these
lines. The emission lines are double peaked with nearly identical strengths of
the violet and red peaks. The H-alpha profile of this star can be successfully
reproduced by our model of a disk seen under an inclination of 30 degrees. In
the case of HD45314, the emission lines are highly asymmetric and display
strong line profile variations. We find a major change in behaviour between the
2002 outburst and the one observed in 2013. This concerns both the relationship
between the equivalent widths of the various lines and their morphologies at
maximum strength (double-peaked in 2002 versus single-peaked in 2013). Our
simple disk model fails to reproduce the observed H-alpha line profiles of
HD45314. Our results further support the interpretation that Oe stars do have
decretion disks similar to those of Be stars. Whilst the emission lines of
HD60848 are explained by a disk with a Keplerian velocity field, the disk of
HD45314 seems to have a significantly more complex velocity field that could be
related to the phenomenon that produces its peculiar X-ray emission.Comment: Accepted for Publication in A&
Worker well-being and the importance of work: bridging the gap
The importance of worker well-being is widely-embraced both in theory and policy, but there are numerous perspectives on what it is, how to measure it, whether it needs improving and if so, how to improve it. We argue that a more complete approach to worker well-being needs to consider workers as full citizens who derive and experience both public and private benefits and costs from working. A broad framework on the meanings of work is used to expand the boundaries of worker well-being to reflect the broad importance of work in human life
Emotions in business-to-business service relationships
Emotion in business-to-business service relationships regarding cargo services is explored. The service relationship is characterised by mutual trust and cooperation. Contact is mainly via telephone or e-mail with some face-to-face interactions and participants providing a complex, multi-skilled seamless service. Experience rather than training plays a vital role with long-term service relationships built up and maintained. Emotional sensitivity is acquired partly by experience and a repeat customer base but mainly through a genuine desire to help and get to know others. In contrast to the view of emotional labour bringing managerial control or adverse affects to service staff, the emotion engendered by this work is authentic expression bringing personal satisfaction
Simultaneous determination of wave speed and arrival time of reflected waves using the pressure-velocity loop
This is the post print version of the article. The official published version can be found at the link below.In a previous paper we demonstrated that the linear portion of the pressure–velocity loop (PU-loop) corresponding to early systole could be used to calculate the local wave speed. In this paper we extend this work to show that determination of the time at which the PU-loop first deviates from linearity provides a convenient way to determine the arrival time of reflected waves (Tr). We also present a new technique using the PU-loop that allows for the determination of wave speed and Tr simultaneously. We measured pressure and flow in elastic tubes of different diameters, where a strong reflection site existed at known distances away form the measurement site. We also measured pressure and flow in the ascending aorta of 11 anaesthetised dogs where a strong reflection site was produced through total arterial occlusion at four different sites. Wave speed was determined from the initial slope of the PU-loop and Tr was determined using a new algorithm that detects the sampling point at which the initial linear part of the PU-loop deviates from linearity. The results of the new technique for detecting Tr were comparable to those determined using the foot-to-foot and wave intensity analysis methods. In elastic tubes Tr detected using the new algorithm was almost identical to that detected using wave intensity analysis and foot-to-foot methods with a maximum difference of 2%. Tr detected using the PU-loop in vivo highly correlated with that detected using wave intensity analysis (r 2 = 0.83, P < 0.001). We conclude that the new technique described in this paper offers a convenient and objective method for detecting Tr, and allows for the dynamic determination of wave speed and Tr, simultaneously
Scanning-probe spectroscopy of semiconductor donor molecules
Semiconductor devices continue to press into the nanoscale regime, and new
applications have emerged for which the quantum properties of dopant atoms act
as the functional part of the device, underscoring the necessity to probe the
quantum structure of small numbers of dopant atoms in semiconductors[1-3].
Although dopant properties are well-understood with respect to bulk
semiconductors, new questions arise in nanosystems. For example, the quantum
energy levels of dopants will be affected by the proximity of nanometer-scale
electrodes. Moreover, because shallow donors and acceptors are analogous to
hydrogen atoms, experiments on small numbers of dopants have the potential to
be a testing ground for fundamental questions of atomic and molecular physics,
such as the maximum negative ionization of a molecule with a given number of
positive ions[4,5]. Electron tunneling spectroscopy through isolated dopants
has been observed in transport studies[6,7]. In addition, Geim and coworkers
identified resonances due to two closely spaced donors, effectively forming
donor molecules[8]. Here we present capacitance spectroscopy measurements of
silicon donors in a gallium-arsenide heterostructure using a scanning probe
technique[9,10]. In contrast to the work of Geim et al., our data show
discernible peaks attributed to successive electrons entering the molecules.
Hence this work represents the first addition spectrum measurement of dopant
molecules. More generally, to the best of our knowledge, this study is the
first example of single-electron capacitance spectroscopy performed directly
with a scanning probe tip[9].Comment: In press, Nature Physics. Original manuscript posted here; 16 pages,
3 figures, 5 supplementary figure
Entanglement in a Solid State Spin Ensemble
Entanglement is the quintessential quantum phenomenon and a necessary
ingredient in most emerging quantum technologies, including quantum repeaters,
quantum information processing (QIP) and the strongest forms of quantum
cryptography. Spin ensembles, such as those in liquid state nuclear magnetic
resonance, have been powerful in the development of quantum control methods,
however, these demonstrations contained no entanglement and ultimately
constitute classical simulations of quantum algorithms. Here we report the
on-demand generation of entanglement between an ensemble of electron and
nuclear spins in isotopically engineered phosphorus-doped silicon. We combined
high field/low temperature electron spin resonance (3.4 T, 2.9 K) with
hyperpolarisation of the 31P nuclear spin to obtain an initial state of
sufficient purity to create a non-classical, inseparable state. The state was
verified using density matrix tomography based on geometric phase gates, and
had a fidelity of 98% compared with the ideal state at this field and
temperature. The entanglement operation was performed simultaneously, with high
fidelity, to 10^10 spin pairs, and represents an essential requirement of a
silicon-based quantum information processor.Comment: 4 pages, 3 figures plus supporting information of 4 pages, 1 figure
v2: Updated reference
KamLAND Sensitivity to Neutrinos from Pre-Supernova Stars
In the late stages of nuclear burning for massive stars (M>8~M_{\sun}), the
production of neutrino-antineutrino pairs through various processes becomes the
dominant stellar cooling mechanism. As the star evolves, the energy of these
neutrinos increases and in the days preceding the supernova a significant
fraction of emitted electron anti-neutrinos exceeds the energy threshold for
inverse beta decay on free hydrogen. This is the golden channel for liquid
scintillator detectors because the coincidence signature allows for significant
reductions in background signals. We find that the kiloton-scale liquid
scintillator detector KamLAND can detect these pre-supernova neutrinos from a
star with a mass of 25~M_{\sun} at a distance less than 690~pc with 3
significance before the supernova. This limit is dependent on the neutrino mass
ordering and background levels. KamLAND takes data continuously and can provide
a supernova alert to the community.Comment: 19 pages, 6 figures, 1 tabl
- …