Quantum phases of bosons in double-well optical lattices

We study the superfluid to Mott insulator transition of bosons in a two-legged ladder optical lattice, of a type accessible in current experiments on double-well optical lattices. The zero-temperature phase diagram is mapped out, with a focus on its dependence upon interchain hopping and the tilt between double wells. We find that the unit-filling Mott phase exhibits a non-monotonic behavior as a function of the tilt parameter, producing a reentrant phase transition between Mott insulator and superfluid phases.Comment: 5 pages, 5 figure

Work-family conflict as a predictor of common mental disorders in the 1958 British birth cohort

© 2015 Society for Longitudinal and Life Course Studies. All rights reserved. The impact of work-family conflict on common mental disorders (CMD) has been examined in cross-sectional studies. The current paper examines work-family conflict and its effect on CMD in a large nationally representative longitudinal sample. This study uses data from the 1958 British birth cohort study, a longitudinal, prospective cohort study of men and women born in a single week in 1958. At 45 years 9,297 individuals were followed up and 9,008 individuals were working. In this sample work-family conflict, sociodemographic factors and the number of hours worked were assessed at age 42 years. The Revised Clinical Interview Schedule (CIS-R) was used to assess CMD, as classified by the International Statistical Classification of Diseases, 10th Revision (ICD-10), in cohort members at age 45 years. Work-family conflict was prospectively associated with an increased risk of common mental disorders (OR=1.76 95% CI 1.36-2.20) adjusting for gender, marital status, social class and educational qualifications. However there was no significant prospective association between the number of hours worked and the prevalence of CMD in this cohort. These results suggest that work-family conflict is a risk factor for future common mental disorder and that in order to prevent common mental disorder this should be considered in job planning. There is a need for more prospective studies with more detailed measures of work-family conflict to confirm these results

The shifted Rayleigh mixture filter for bearings-only tracking of maneuvering targets

Published versio

Commuting Quantum Circuits with Few Outputs are Unlikely to be Classically Simulatable

We study the classical simulatability of commuting quantum circuits with n input qubits and O(log n) output qubits, where a quantum circuit is classically simulatable if its output probability distribution can be sampled up to an exponentially small additive error in classical polynomial time. First, we show that there exists a commuting quantum circuit that is not classically simulatable unless the polynomial hierarchy collapses to the third level. This is the first formal evidence that a commuting quantum circuit is not classically simulatable even when the number of output qubits is exponentially small. Then, we consider a generalized version of the circuit and clarify the condition under which it is classically simulatable. Lastly, we apply the argument for the above evidence to Clifford circuits in a similar setting and provide evidence that such a circuit augmented by a depth-1 non-Clifford layer is not classically simulatable. These results reveal subtle differences between quantum and classical computation.Comment: 19 pages, 6 figures; v2: Theorems 1 and 3 improved, proofs modifie

Real-time national GPS networks: Opportunities for atmospheric sensing

Real-time national Global Positioning System (GPS) networks are being established in a number of countries for atmospheric sensing. UCAR, in collaboration with participating universities, is developing one of these networks in the United States. The network, named "SuomiNet" to honor meteorological satellite pioneer Verner Suomi, is funded by the U.S. National Science Foundation. SuomiNet will exploit the recently-shown ability of ground-based GPS receivers to make thousands of accurate upper and lower atmospheric measurements per day. Phase delays induced in GPS signals by the ionosphere and neutral atmosphere can be measured with high precision simultaneously along up to a dozen GPS ray paths in the field of view. These delays can be converted into total electron content (TEC), and integrated water vapor (if surface pressure data or estimates are available), along each GPS ray path. The resulting continuous, accurate, all-weather, real-time upper and lower atmospheric data create a variety of opportunities for atmospheric research. In this letter we describe SuomiNet, its applications, and the opportunity to coordinate national real-time GPS networks to create, a global network with larger scientific and operational potential. Copy right© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences

Palliative care making a difference in rural Uganda, Kenya and Malawi: three rapid evaluation field studies

<p>Abstract</p> <p>Background</p> <p>Many people live and die in pain in Africa. We set out to describe patient, family and local community perspectives on the impact of three community based palliative care interventions in sub-Saharan Africa.</p> <p>Methods</p> <p>Three palliative care programmes in Uganda, Kenya and Malawi were studied using rapid evaluation field techniques in each country, triangulating data from three sources: <b><it>interviews </it></b>with key informants, <b><it>observations </it></b>of clinical encounters and the local health and social care context, and routine data from local <b><it>reports and statistics</it></b>.</p> <p>Results</p> <p>We interviewed 33 patients with advanced illness, 27 family carers, 36 staff, 25 volunteers, and 29 community leaders and observed clinical care of 12 patients. In each site, oral morphine was being used effectively. Patients valued being treated with dignity and respect. Being supported at home reduced physical, emotional and financial burden of travel to, and care at health facilities. Practical support and instruction in feeding and bathing patients facilitated good deaths at home.</p> <p>In each country mobile phones enabled rapid access to clinical and social support networks. Staff and volunteers generally reported that caring for the dying in the face of poverty was stressful, but also rewarding, with resilience fostered by having effective analgesia, and community support networks.</p> <p>Conclusions</p> <p>Programmes were reported to be successful because they integrated symptom control with practical and emotional care, education, and spiritual care. Holistic palliative care can be delivered effectively in the face of poverty, but a public health approach is needed to ensure equitable provision.</p

Holocene fire regimes and treeline migration rates in sub-arctic Canada

Holocene climate change resulted in major vegetation reorganization in sub-arctic Canada near modern treeline. However, little is known of the effects of long-term climate change on boreal forest composition and fire regimes below treeline in this region. We present a high-resolution vegetation and fire history from two sites within the modern boreal forest in the central Northwest Territories, Canada, to provide new insight on sub-arctic vegetation response to Holocene climate dynamics and the role of fire in boreal ecosystems. Palynological analysis of sediments retrieved from Waite and Danny's lakes (informal) is used to reconstruct regional vegetation dynamics and boreal fire regimes. The longer Danny's Lake record documents treeline expansion beginning at ca. 7430–7220 cal yr BP. Integration of our new data with previous work shows that treeline expanded between ca. 4050 cal. yr BP and ca. 3840 cal yr BP at a rate of ca. 50 m/yr in response to the 1–2 °C increase in temperature estimated for the Holocene Thermal Maximum. Forest fires were relatively frequent during the early Holocene, before declining in frequency in response to development of cooler and wetter climate conditions associated with the Neoglacial (beginning after ca. 2200–2320 cal yr BP). We document a trend of increasing fire frequency in the 20th century that is correlated with warming at this time. These dynamics south of modern treeline provide insight into factors creating heterogeneity in plant community responses to large-scale climate events in high northern latitudes and suggest that large scale reorganization of boreal vegetation and fire regimes can be expected over the coming decades