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We demonstrated an optimization of a picosecond fiber amplifier based on Yb-doped tapered fiber in a spectral range of 1030 nm. Nonlinear effects limiting peak power scaling (stimulated Raman scattering and four-wave mixing) were studied and factors affecting their threshold were established, such as gain, diameter profile along the length of taper, output mode field diameter, and numerical aperture of a pump. By determining the optimal amplification regime and manufacturing advanced tapered fibers, we amplified 13 ps pulses to a record-high peak power of 1 MW at a wavelength of 1029 nm directly at the output of the fiber at an average power of 13.8 W. Four-wave mixing was the limiting factor, and the total fraction of deleterious components in the output spectrum was ~2%. The quality of the output beam was close to being diffraction limited (M2 < 1.2).

The possibility to scale-up output pulse energy in diffraction-limited Er-doped fiber amplifier has been studied. It is shown that the utilization of tapered fiber design allows one to increase the pulse energy up to 2 mJ, while keeping the diffraction-limited beam quality (M2~1.4). Factors limiting the further increase in pulse energy are revealed.

A tapered Er-doped fiber amplifier for high peak power pulses amplification has been developed and tested. The core diameter changed from 15.8 µm (mode field diameter (MFD) 14.5 µm) to 93 µm (MFD 40 µm) along 3.7 m maintaining single-mode performance at 1555 nm (according to the S2-method, the part of the power of high-order modes does not exceed 1.5%). The amplification of 0.9 ns pulses with spectral width below 0.04 nm up to a peak power above 200 kW (limited by self-phase modulation) with a slope pump-to-signal conversion efficiency of 15.6% was demonstrated.

Prospects for average power scaling of sub-MW output peak power picosecond fiber lasers by utilization of a Yb-doped tapered fiber at the final amplification stage were studied. In this paper, it was shown experimentally that a tapered fiber allows the achievement of an average power level of 150 W (limited by the available pump power) with a peak power of 0.74 MW for 22 ps pulses with no signs of transverse mode instability. Measurements of the mode content using the S 2 technique showed a negligible level of high order modes (less than 0.3%) in the output radiation even for the maximum output power level. Our reliability tests predict no thermal issues during long-term operation (10 5 hours) of the developed tapered fiber laser up to kilowatt output average power levels.

Background: Faster off-rate competitive enzyme inhibitors are generally more sensitive than slower off-rate ones to binding inhibition by enzyme substrates. We previously reported that the cyclic adenosine monophosphate concentration in dopamine D1 receptor-expressing medium spiny neurons (D1-MSNs) may be higher than that in D2-MSNs. Consequently, compared with slower off-rate phosphodiesterase 10A inhibitors, faster off-rate ones comparably activated D2-MSNs but partially activated D1-MSNs. We further investigated the pharmacological profiles of phosphodiesterase 10A inhibitors with different off-rates., Methods: Phosphodiesterase 10A inhibitors with slower (T-609) and faster (T-773) off-rates were used. D1- and D2-MSN activation was assessed by substance P and enkephalin mRNA induction, respectively, in rodents. Antipsychotic-like effects were evaluated by MK-801- and methamphetamine-induced hyperactivity and prepulse inhibition in rodents. Cognition was assessed by novel object recognition task and radial arm maze in rats. Prefrontal cortex activation was evaluated by c-Fos immunohistochemistry in rats. Gene translations in D1- and D2-MSNs were evaluated by translating ribosome affinity purification and RNA sequencing in mice., Results: Compared with T-609, T-773 comparably activated D2-MSNs but partially activated D1-MSNs. Haloperidol (a D2 antagonist) and T-773, but not T-609, produced antipsychotic-like effects in all paradigms. T-773, but not T-609 or haloperidol, activated the prefrontal cortex and improved cognition. Overall gene translation patterns in D2-MSNs by all drugs and those in D1-MSNs by T-773 and T-609 were qualitatively similar., Conclusions: Differential pharmacological profiles among those drugs could be attributable to activation balance of D1- and D2-MSNs. The "balanced activation" of MSNs by faster off-rate phosphodiesterase 10A inhibitors may be favorable to treat schizophrenia., (© The Author(s) 2019. Published by Oxford University Press on behalf of CINP.)

We demonstrate a novel amplification regime in a counter-pumped, relatively long (2 meters), large mode area, highly Yb-doped and polarization-maintaining tapered fiber, which offers a high peak power directly from the amplifier. The main feature of this regime is that the amplifying signal propagates through a thin part of the tapered fiber without amplification and experiences an extremely high gain in the thick part of the tapered fiber, where most of the pump power is absorbed. In this regime, we have demonstrated 8 ps pulse amplification to a peak power of up to 0.76 MW, which is limited by appearance of stimulated Raman scattering. In the same regime, 28 ps chirped pulses are amplified to a peak power of 0.35 MW directly from the amplifier and then compressed with 70% efficiency to 315 ± 10 fs, corresponding to an estimated peak power of 22 MW.

We introduce NSeq, a fast and efficient Java application for finding positioned nucleosomes from the high-throughput sequencing of MNase-digested mononucleosomal DNA. NSeq includes a user-friendly graphical interface, computes false discovery rates (FDRs) for candidate nucleosomes from Monte Carlo simulations, plots nucleosome coverage and centers, and exploits the availability of multiple processor cores by parallelizing its computations. Java binaries and source code are freely available at https://github.com/songlab/NSeq. The software is supported on all major platforms equipped with Java Runtime Environment 6 or later.