31 research outputs found
Theory of coherent Bragg spectroscopy of a trapped Bose-Einstein condensate
We present a detailed theoretical analysis of Bragg spectroscopy from a
Bose-Einstein condensate at T=0K. We demonstrate that within the linear
response regime, both a quantum field theory treatment and a meanfield
Gross-Pitaevskii treatment lead to the same value for the mean evolution of the
quasiparticle operators. The observable for Bragg spectroscopy experiments,
which is the spectral response function of the momentum transferred to the
condensate, can therefore be calculated in a meanfield formalism. We analyse
the behaviour of this observable by carrying out numerical simulations in
axially symmetric three-dimensional cases and in two dimensions. An approximate
analytic expression for the observable is obtained and provides a means for
identifying the relative importance of three broadening and shift mechanisms
(meanfield, Doppler, and finite pulse duration) in different regimes. We show
that the suppression of scattering at small values of q observed by
Stamper-Kurn et al. [Phys. Rev. Lett. 83, 2876 (1999)] is accounted for by the
meanfield treatment, and can be interpreted in terms of the interference of the
u and v quasiparticle amplitudes. We also show that, contrary to the
assumptions of previous analyses, there is no regime for trapped condensates
for which the spectral response function and the dynamic structure factor are
equivalent. Our numerical calculations can also be performed outside the linear
response regime, and show that at large laser intensities a significant
decrease in the shift of the spectral response function can occur due to
depletion of the initial condensate.Comment: RevTeX4 format, 16 pages plus 7 eps figures; Update to published
version: minors changes and an additional figure. (To appear in Phys. Rev. A
Momentum state engineering and control in Bose-Einstein condensates
We demonstrate theoretically the use of genetic learning algorithms to
coherently control the dynamics of a Bose-Einstein condensate. We consider
specifically the situation of a condensate in an optical lattice formed by two
counterpropagating laser beams. The frequency detuning between the lasers acts
as a control parameter that can be used to precisely manipulate the condensate
even in the presence of a significant mean-field energy. We illustrate this
procedure in the coherent acceleration of a condensate and in the preparation
of a superposition of prescribed relative phase.Comment: 9 pages incl. 6 PostScript figures (.eps), LaTeX using RevTeX,
submitted to Phys. Rev. A, incl. small modifications, some references adde
The Pediatric Cell Atlas: defining the growth phase of human development at single-cell resolution
Single-cell gene expression analyses of mammalian tissues have uncovered profound stage-specific molecular regulatory phenomena that have changed the understanding of unique cell types and signaling pathways critical for lineage determination, morphogenesis, and growth. We discuss here the case for a Pediatric Cell Atlas as part of the Human Cell Atlas consortium to provide single-cell profiles and spatial characterization of gene expression across human tissues and organs. Such data will complement adult and developmentally focused HCA projects to provide a rich cytogenomic framework for understanding not only pediatric health and disease but also environmental and genetic impacts across the human lifespan
23rd IAEA Fusion Energy Conference: summary of sessions EX/C and ICC
An overview is given of recent experimental results in the areas of innovative confinement concepts, operational scenarios and confinement experiments as presented at the 2010 IAEA Fusion Energy Conference. Important new findings are presented from fusion devices worldwide, with a strong focus towards the scientific and technical issues associated with ITER and W7-X devices, presently under construction
Effects of rare kidney diseases on kidney failure: a longitudinal analysis of the UK National Registry of Rare Kidney Diseases (RaDaR) cohort
Background
Individuals with rare kidney diseases account for 5–10% of people with chronic kidney disease, but constitute more than 25% of patients receiving kidney replacement therapy. The National Registry of Rare Kidney Diseases (RaDaR) gathers longitudinal data from patients with these conditions, which we used to study disease progression and outcomes of death and kidney failure.
Methods
People aged 0–96 years living with 28 types of rare kidney diseases were recruited from 108 UK renal care facilities. The primary outcomes were cumulative incidence of mortality and kidney failure in individuals with rare kidney diseases, which were calculated and compared with that of unselected patients with chronic kidney disease. Cumulative incidence and Kaplan–Meier survival estimates were calculated for the following outcomes: median age at kidney failure; median age at death; time from start of dialysis to death; and time from diagnosis to estimated glomerular filtration rate (eGFR) thresholds, allowing calculation of time from last eGFR of 75 mL/min per 1·73 m2 or more to first eGFR of less than 30 mL/min per 1·73 m2 (the therapeutic trial window).
Findings
Between Jan 18, 2010, and July 25, 2022, 27 285 participants were recruited to RaDaR. Median follow-up time from diagnosis was 9·6 years (IQR 5·9–16·7). RaDaR participants had significantly higher 5-year cumulative incidence of kidney failure than 2·81 million UK patients with all-cause chronic kidney disease (28% vs 1%; p<0·0001), but better survival rates (standardised mortality ratio 0·42 [95% CI 0·32–0·52]; p<0·0001). Median age at kidney failure, median age at death, time from start of dialysis to death, time from diagnosis to eGFR thresholds, and therapeutic trial window all varied substantially between rare diseases.
Interpretation
Patients with rare kidney diseases differ from the general population of individuals with chronic kidney disease: they have higher 5-year rates of kidney failure but higher survival than other patients with chronic kidney disease stages 3–5, and so are over-represented in the cohort of patients requiring kidney replacement therapy. Addressing unmet therapeutic need for patients with rare kidney diseases could have a large beneficial effect on long-term kidney replacement therapy demand.
Funding
RaDaR is funded by the Medical Research Council, Kidney Research UK, Kidney Care UK, and the Polycystic Kidney Disease Charity
Safety of milrinone use in neonatal intensive care units
Background: Milrinone use in the neonatal intensive care unit has increased over the last 10. years despite a paucity of published safety data in infants. We sought to determine the safety of milrinone therapy among infants in the neonatal intensive care unit. Methods: We conducted a retrospective data analysis, identifying all infants who were exposed to milrinone and discharged from 322 neonatal intensive care units managed by the Pediatrix Medical Group from 1997-2010. We identified adverse events (AEs) during milrinone exposure. The unit of observation for clinical AEs was the first course of milrinone and for laboratory AEs it was an infant-day of exposure to milrinone. Results: Overall, 1446 of 716,821 (0.2%) infants received milrinone for a total of 6894 infant-days. The proportion of infants exposed to milrinone increased from 0 in 1997 to 4/1000 infant cases in 2010. Persistent pulmonary hypertension (40%) was the most commonly reported diagnosis at the start of milrinone administration. Overall, 606/1446 (42%) of infants had at least 1 clinical AE recorded during milrinone therapy. Hypotension requiring pressors and thrombocytopenia (<100,000/mm3) were the most commonly reported clinical and laboratory AEs, respectively. Death was reported in 8% of infants during the first course of milrinone therapy. Conclusion: Among infants hospitalized in the neonatal intensi