307 research outputs found
Spectral Line-by-Line Pulse Shaping of an On-Chip Microresonator Frequency Comb
We report, for the first time to the best of our knowledge, spectral phase
characterization and line-by-line pulse shaping of an optical frequency comb
generated by nonlinear wave mixing in a microring resonator. Through
programmable pulse shaping the comb is compressed into a train of
near-transform-limited pulses of \approx 300 fs duration (intensity full width
half maximum) at 595 GHz repetition rate. An additional, simple example of
optical arbitrary waveform generation is presented. The ability to characterize
and then stably compress the frequency comb provides new data on the stability
of the spectral phase and suggests that random relative frequency shifts due to
uncorrelated variations of frequency dependent phase are at or below the 100
microHertz level.Comment: 18 pages, 4 figure
Ultrafast imaging of the entire chest without ECG synchronisation or beta-blockade: to what extent can we analyse the coronary arteries?
Temperature measurement and stabilization in a birefringent whispering gallery resonator
Temperature measurement with nano-Kelvin resolution is demonstrated at room
temperature, based on the thermal dependence of an optical crystal anisotropy
in a high quality whispering gallery resonator. As the resonator's TE and TM
modes frequencies have different temperature coefficients, their differential
shift provides a sensitive measurement of the temperature variation, which is
used for active stabilization of the temperature
Acceleration of generalized hypergeometric functions through precise remainder asymptotics
We express the asymptotics of the remainders of the partial sums {s_n} of the
generalized hypergeometric function q+1_F_q through an inverse power series z^n
n^l \sum_k c_k/n^k, where the exponent l and the asymptotic coefficients {c_k}
may be recursively computed to any desired order from the hypergeometric
parameters and argument. From this we derive a new series acceleration
technique that can be applied to any such function, even with complex
parameters and at the branch point z=1. For moderate parameters (up to
approximately ten) a C implementation at fixed precision is very effective at
computing these functions; for larger parameters an implementation in higher
than machine precision would be needed. Even for larger parameters, however,
our C implementation is able to correctly determine whether or not it has
converged; and when it converges, its estimate of its error is accurate.Comment: 36 pages, 6 figures, LaTeX2e. Fixed sign error in Eq. (2.28), added
several references, added comparison to other methods, and added discussion
of recursion stabilit
Serous cystic neoplasm of the pancreas: A multinational study of 2622 patients under the auspices of the International Association of Pancreatology and European Pancreatic Club (European Study Group on Cystic Tumors of the Pancreas)
OBJECTIVES:
Serous cystic neoplasm (SCN) is a cystic neoplasm of the pancreas whose natural history is poorly known. The purpose of the study was to attempt to describe the natural history of SCN, including the specific mortality.
DESIGN:
Retrospective multinational study including SCN diagnosed between 1990 and 2014.
RESULTS:
2622 patients were included. Seventy-four per cent were women, and median age at diagnosis was 58\u2005years (16-99). Patients presented with non-specific abdominal pain (27%), pancreaticobiliary symptoms (9%), diabetes mellitus (5%), other symptoms (4%) and/or were asymptomatic (61%). Fifty-two per cent of patients were operated on during the first year after diagnosis (median size: 40\u2005mm (2-200)), 9% had resection beyond 1\u2005year of follow-up (3\u2005years (1-20), size at diagnosis: 25\u2005mm (4-140)) and 39% had no surgery (3.6\u2005years (1-23), 25.5\u2005mm (1-200)). Surgical indications were (not exclusive) uncertain diagnosis (60%), symptoms (23%), size increase (12%), large size (6%) and adjacent organ compression (5%). In patients followed beyond 1\u2005year (n=1271), size increased in 37% (growth rate: 4\u2005mm/year), was stable in 57% and decreased in 6%. Three serous cystadenocarcinomas were recorded. Postoperative mortality was 0.6% (n=10), and SCN's related mortality was 0.1% (n=1).
CONCLUSIONS:
After a 3-year follow-up, clinical relevant symptoms occurred in a very small proportion of patients and size slowly increased in less than half. Surgical treatment should be proposed only for diagnosis remaining uncertain after complete workup, significant and related symptoms or exceptionally when exists concern with malignancy. This study supports an initial conservative management in the majority of patients with SCN
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