6,066 research outputs found
Beyond balancing? Intrastate conflict and US grand strategy
ArticleThis is the author accepted manuscript. The final version is available from Taylor & Francis (Routledge) via the DOI in this record.Grand strategic theorists share an historical emphasis on interstate conflict. However,
of some two hundred and seventy-three US military deployments since 1900, only seven were
interstate conflicts. The rest were intrastate, domestic level engagements. We argue that these
intrastate conflicts limit the utility of regional balances of power in mitigating forms of conflict
that the US may consider inimical to its national security interests. When considering potential
changes to US force posture and grand strategy, American coercive statecraft should be theorised
along a broader strategic continuum encompassing the full range of conflict
Security Leverage, Structural power and US Strategy in East Asia
This is the author accepted manuscript. The final version is available from OUP via the DOI in this record.What is the utility of US military power when seeking to generate international economic arrangements conducive to its national interests? Developing the concepts of positive and negative structural power we argue that regional American primacy in East Asia has allowed it to leverage its military power into generating political-economic institutional outcomes that have reinforced its broader leadership role. The US may well continue its deep engagement or follow a path of retrenchment under President Trump. Both grand strategic options will impact on its capacity to leverage its positive and negative structural power and have implications for US hegemony and the region’s political economy
Extending the aridity record of the Southwest Kalahari: current problems and future perspectives
An extensive luminescence-based chronological framework has allowed the reconstruction of expansions and contractions of the Kalahari Desert over the last 50 ka. However, this chronology is largely based on near-surface pits and sediment exposures. These are the points on the landscape most prone to reactivation and resetting of the luminescence dating ‘clock’. This is proving to be a limiting feature for extending palaeoenvironmental reconstructions further back in time. One way to obviate this is to sample desert marginal areas that only become active during significant arid phases. An alternative is to find and sample deep stratigraphic exposures. The Mamatwan manganese mine at Hotazel in the SW Kalahari meets both these criteria. Luminescence dating of this site shows the upper sedimentary unit to span at least the last 60 ka with tentative age estimates from underlying cemented aeolian units dating back to the last interglacial and beyond. Results from Mamatwan are comparable to new and previously published data from linear dunes in the SW Kalahari but extend back much further. Analysis of the entire data set of luminescence ages for the SW Kalahari brings out important inferences that suggest that different aeolian forms (1) have been active over different time scales in the past, (2) have different sensitivities to environmental changes and (3) have different time scales over which they record and preserve the palaeoenvironmental record. This implies that future optically stimulated luminescence work and palaeoenvironmental reconstructions must consider both site location and its relationship to desert margins and sediment depositional styles, so that the resolution and duration of the aridity record can be optimally understood
Observation of sub-Poisson photon statistics in the cavity-QED microlaser
We have measured the second-order correlation function of the cavity-QED
microlaser output and observed a transition from photon bunching to
antibunching with increasing average number of intracavity atoms. The observed
correlation times and the transition from super- to sub-Poisson photon
statistics can be well described by gain-loss feedback or enhanced/reduced
restoring action against fluctuations in photon number in the context of a
quantum microlaser theory and a photon rate equation picture. However, the
theory predicts a degree of antibunching several times larger than that
observed, which may indicate the inadequacy of its treatment of atomic velocity
distributions.Comment: 4 pages, 4 figure
Measuring atomic NOON-states and using them to make precision measurements
A scheme for creating NOON-states of the quasi-momentum of ultra-cold atoms
has recently been proposed [New J. Phys. 8, 180 (2006)]. This was achieved by
trapping the atoms in an optical lattice in a ring configuration and rotating
the potential at a rate equal to half a quantum of angular momentum . In this
paper we present a scheme for confirming that a NOON-state has indeed been
created. This is achieved by spectroscopically mapping out the anti-crossing
between the ground and first excited levels by modulating the rate at which the
potential is rotated. Finally we show how the NOON-state can be used to make
precision measurements of rotation.Comment: 14 preprint pages, 7 figure
Qudit Quantum State Tomography
Recently quantum tomography has been proposed as a fundamental tool for
prototyping a few qubit quantum device. It allows the complete reconstruction
of the state produced from a given input into the device. From this
reconstructed density matrix, relevant quantum information quantities such as
the degree of entanglement and entropy can be calculated. Generally orthogonal
measurements have been discussed for this tomographic reconstruction. In this
paper, we extend the tomographic reconstruction technique to two new regimes.
First we show how non-orthogonal measurement allow the reconstruction of the
state of the system provided the measurements span the Hilbert space. We then
detail how quantum state tomography can be performed for multi qudits with a
specific example illustrating how to achieve this in one and two qutrit
systems.Comment: 6 pages, 4 figures, submitted to PR
Operational Change and American Grand Strategy in the Context of the China Challenge
This is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this record.With fiscal pressures at home and China’s continued rise abroad, the United States shows no
signs of wanting to reverse its costly grand strategy of deep engagement. In the context of
America’s relative decline, we evaluate existing proposals to ease pressures on the United States.
We argue that the key aspects of American decline are in fact often operational rather than
strategic in nature, consequently the undifferentiated fashion in which rise and decline is often
presented is neither useful in describing current changes nor in proposing how to address them.
Problems at the operational level do not necessarily demand higher-level strategic level
alterations. As such, while restructured forms of deep engagement will help alleviate resource
constraints in the medium to long term, their utility in addressing the operational changes
brought on by relative decline are less apparent. Given that resource constraints are therefore
not necessarily the primary concern, the major strategic elements of American deep engagement
are more durable than commonly supposed. America’s current strategic objectives are not
constrained by changes brought on by its relative material decline with respect to China, but by
changes in the operational environment
Dynamics of a trapped Brownian particle in shear flows
The Brownian motion of a particle in a harmonic potential, which is
simultaneously exposed either to a linear shear flow or to a plane Poiseuille
flow is investigated. In the shear plane of both flows the probability
distribution of the particle becomes anisotropic and the dynamics is changed in
a characteristic manner compared to a trapped particle in a quiescent fluid.
The particle distribution takes either an elliptical or a parachute shape or a
superposition of both depending on the mean particle position in the shear
plane. Simultaneously, shear-induced cross-correlations between particle
fluctuations along orthogonal directions in the shear plane are found. They are
asymmetric in time. In Poiseuille flow thermal particle fluctuations
perpendicular to the flow direction in the shear plane induce a shift of the
particle's mean position away from the potential minimum. Two complementary
methods are suggested to measure shear-induced cross-correlations between
particle fluctuations along orthogonal directions.Comment: 14 pages, 7 figure
Intrinsic neuronal dynamics predict distinct functional roles during working memory
Working memory (WM) is characterized by the ability to maintain stable representations over time; however, neural activity associated with WM maintenance can be highly dynamic. We explore whether complex population coding dynamics during WM relate to the intrinsic temporal properties of single neurons in lateral prefrontal cortex (lPFC), the frontal eye fields (FEF), and lateral intraparietal cortex (LIP) of two monkeys (Macaca mulatta). We find that cells with short timescales carry memory information relatively early during memory encoding in lPFC; whereas long-timescale cells play a greater role later during processing, dominating coding in the delay period. We also observe a link between functional connectivity at rest and the intrinsic timescale in FEF and LIP. Our results indicate that individual differences in the temporal processing capacity predict complex neuronal dynamics during WM, ranging from rapid dynamic encoding of stimuli to slower, but stable, maintenance of mnemonic information.Biotechnology and Biological Sciences Research Council (Great Britain) (BB/M010732/1)United States. Office of Naval Research (N00014-14-1-0681)National Institute of Mental Health (U.S.) (R00MH092715)National Institute of Mental Health (U.S.) (R37MH087027)Massachusetts Institute of Technology. Picower Innovation FundUnited States. Office of Naval Research. Multidisciplinary University Research Initiative (grant N00014-16-1-2832)National Institute for Health Research (Great Britain). Wellcome Trust (203139/Z/16/Z
Improving Effective Surgical Delivery in Humanitarian Disasters: Lessons from Haiti
Kathryn Chu and colleagues describe the experiences of Médecins sans Frontières after the 2010 Haiti earthquake, and discuss how to improve delivery of surgery in humanitarian disasters
- …