Validation of a zebrafish developmental defects assay as a qualified alternative test for its regulatory use following the ICH S5(R3) guideline.

Zebrafish is a popular toxicology model and provides an ethically acceptable small-scale analysis system with the complexity of a complete organism. Our goal is to further validate this model for its regulatory use for reproductive and developmental defects by testing the compounds indicated in the "Guideline on detection of reproductive and developmental toxicity for human pharmaceuticals" (ICH S5(R3) guideline.) To determine the embryotoxic and developmental risk of the 32 reference compounds listed in the ICH S5(R3) guideline, the presence of morphological alterations in zebrafish embryos was analyzed at two different stages to calculateLC50 and EC50 values for each stage. Teratogenic Indexes were established as the ratio between LC50 and EC50 critical for the proper compound classification as teratogenic when it is ≥ 2. A total of three biological replicates have been conducted to study the reproducibility of the assay. The chemicals' concentration in the medium and internally in the zebrafish embryos was evaluated. In this study, the 3 negative compounds were properly categorized while 23 compounds out of the 29 reference ones (sensitivity of 79.31%) were classified as teratogenic in zebrafish. The 6 that had false-negative results were classified 4 as inconclusive, 1 as not toxic, and 1 compound resulted toxic for zebrafish embryos under testing conditions. After the bioavailability experiments, some of the obtained inconclusive results were refined. The developmental defects assay in zebrafish gives an accuracy of 89.66%, sensitivity of 88.46%, specificity and repeatability of 100% compared to mammals; therefore, this is a well-integrated strategy using New Alternative Methods, to minimize the use of animals in developmental toxicity studies.

Efficient compressive and Bayesian characterization of biphoton frequency spectra.

Frequency-bin qudits constitute a promising tool for quantum information processing, but their high dimensionality can make for tedious characterization measurements. Here we introduce and compare compressive sensing and Bayesian mean estimation for recovering the spectral correlations of entangled photon pairs. Using a conventional compressive sensing algorithm, we reconstruct joint spectra with up to a 26-fold reduction in measurement time compared to the equivalent raster scan. Applying a custom Bayesian model to the same data, we then additionally realize reliable and consistent quantification of uncertainty. These efficient methods of biphoton characterization should advance our ability to use the high degree of parallelism and complexity afforded by frequency-bin encoding.

Broadly tunable, low timing jitter, high repetition rate optoelectronic comb generator.

We investigate the low timing jitter properties of a tunable single-pass optoelectronic frequency comb generator. The scheme is flexible in that both the repetition rate and center frequency can be continuously tuned. When operated with 10 GHz comb spacing, the integrated residual pulse-to-pulse timing jitter is 11.35 fs (1 Hz to 10 MHz) with no feedback stabilization. The corresponding phase noise at 1 Hz offset from the photodetected 10 GHz carrier is -100 dBc/Hz.

Dual-comb electric-field cross-correlation technique for optical arbitrary waveform characterization.

We present an electric-field cross-correlation technique that uses a pair of frequency combs to sweep phase and group delays independently without a mechanical stage. We demonstrate this technique for characterization of optical arbitrary waveforms composed of ~30 spectral lines from a 10 GHz frequency comb. Rapid data acquisition (tens of microseconds) enables interferometric spectral phase measurement of pulses subject to propagation over 20 km of optical fiber.

Generation of 20 GHz, sub-40 fs pulses at 960 nm via repetition-rate multiplication.

Optical filtering of a stabilized 1 GHz optical frequency comb produces a 20 GHz comb with approximately 40 nm bandwidth (FWHM) at 960 nm. Use of a low-finesse Fabry-Pérot cavity in a double-pass configuration provides a broad cavity coupling bandwidth (Deltalambda/lambda approximately 10%) and large suppression (50 dB) of unwanted modes. Pulse durations shorter than 40 fs with less than 2% residual amplitude modulation are achieved.

Improved signal-to-noise ratio of 10 GHz microwave signals generated with a mode-filtered femtosecond laser frequency comb.

We use a Fabry-Perot cavity to optically filter the output of a Ti:sapphire frequency comb to integer multiples of the original 1 GHz mode spacing. This effectively increases the pulse repetition rate, which is useful for several applications. In the case of low-noise microwave signal generation, such filtering leads to improved linearity of the high-speed photodiodes that detect the mode-locked laser pulse train. The result is significantly improved signal-to-noise ratio at the 10 GHz harmonic with the potential for a shot-noise limited single sideband phase noise floor near -168 dBc/Hz.

Interferometry from a scattering medium.

A two-beam random interferometer is demonstrated where coupling is facilitated by a scattering medium. A modulation observed in the normalized second-order intensity frequency correlation of the transmitted light is attributed to the relative temporal delay of the two beams and is insensitive to beam alignment and spacing.

CNBP mediates neural crest cell expansion by controlling cell proliferation and cell survival during rostral head development.

Striking conservation in various organisms suggests that cellular nucleic acid binding protein (CNBP) plays a fundamental biological role across different species. Recently, it was reported that CNBP is required for forebrain formation during chick and mouse embryogenesis. In this study, we have used the zebrafish model system to expand and contextualize the basic understanding of the molecular mechanisms of CNBP activity during vertebrate head development. We show that zebrafish cnbp is expressed in the anterior CNS in a similar fashion as has been observed in early chick and mouse embryos. Using antisense morpholino oligonucleotide knockdown assays, we show that CNBP depletion causes forebrain truncation while trunk development appears normal. A substantial reduction in cell proliferation and an increase in cell death were observed in the anterior regions of cnbp morphant embryos, mainly within the cnbp expression territory. In situ hybridization assays show that CNBP depletion does not affect CNS patterning while it does cause depletion of neural crest derivatives. Our data suggest an essential role for CNBP in mediating neural crest expansion by controlling proliferation and cell survival rather than via a cell fate switch during rostral head development. This possible role of CNBP may not only explain the craniofacial anomalies observed in zebrafish but also those reported for mice and chicken and, moreover, demonstrates that CNBP plays an essential and conserved role during vertebrate head development.

Programmable polarization-independent spectral phase compensation and pulse shaping by use of a single-layer liquid-crystal modulator.

What we believe to be the first use of a single-layer liquid-crystal modulator array for spectral phase pulse shaping that operates independently of input polarization is reported. Polarization insensitivity is essential to optical-fiber-based applications such as dispersion compensation.

Wideband all-order polarization mode dispersion compensation via pulse shaping.

We demonstrate the application of ultrafast pulse-shaping techniques for experimental wideband all-order polarization mode dispersion (PMD) compensation, for the first time to our knowledge. PMD is treated as arbitrary variations of state of polarization and phase versus wavelength, in an all-order sense. Consequently, two pulse shapers are implemented in a serial manner to compensate for the polarization and the phase spectra independently. We report compensation of subpicosecond pulses (14 nm bandwidth around 1550 nm) that are anomalously spread to more than 2 ps as a result of PMD. This PMD compensation scheme can potentially be a powerful and cost-effective solution for fiber optic telecommunication networks.

Fully dispersion-compensated approximately 500 fs pulse transmission over 50 km single-mode fiber.

We demonstrate essentially distortionless 50 km fiber transmission for approximately 500 fs pulses, using dispersion-compensating fiber and a programmable pulse shaper as a spectral phase equalizer. This distance is approximately five times longer than previously achieved at similar pulse widths.

Spectral line-by-line pulse shaping.

We experimentally demonstrate pulse-shaping experiments in which the individual spectral lines that are present in the output of a mode-locked laser (8.5 GHz mode spacing, centered at 1542 nm) are resolved. The shaped pulses overlap in time, and this leads to a new way to observe fluctuations of the comb-offset frequency in the time domain.

Line-by-line pulse shaping control for optical arbitrary waveform generation.

We demonstrate a fundamental operation for generating complex waveforms in the optical domain - line-by-line pulse shaping control for optical arbitrary waveform generation (O-AWG). Independent manipulation of the spectral amplitude and phase of individual lines from a mode-locked frequency comb, or spectral line-by-line pulse shaping, leads to synthesis of user-specified ultrafast optical waveforms with unprecedented control. Coupled with recent advances in frequency stabilized mode-locked lasers, line-by-line pulse shaping control should have significant impact to fields drawing upon developments in the field of ultrafast science.

Pulse shaper in a loop: demonstration of cascadable ultrafast all-optical code translation.

We experimentally demonstrate repetitive M-ary spectral phase pulse shaping by placing a programmable pulse shaper driven by a 10-GHz source in a closed loop. This permits generation of encoded and decoded signals in the same apparatus by forming a closed loop to circulate a part of the output back into the pulse shaper. As a result, a series of M - 1 distinct encoded waveforms is sequentially generated, followed by generation of a properly decoded pulse.

Spectral and temporal speckle field measurements of a random medium.

The zero-mean circular complex Gaussian field statistics of a random medium are experimentally demonstrated in the optical domain, thus verifying this key assumption of statistical optics. Using a frequency-tunable laser source in a fixed-path-length interferometer, we obtain optical field fluctuations in the time and frequency domains that clearly show that the ensemble-averaged temporal intensity converges to the photon transit time distribution, which for the samples used is in excellent agreement with a diffusion model.

Femtosecond direct space-to-time pulse shaping in an integrated-optic configuration.

We demonstrate femtosecond operation of an integrated-optic direct space-to-time pulse shaper for which there is a direct mapping (no Fourier transform) between the spatial position of the masking function and the temporal position in the output waveform. The apparatus is used to generate trains of more than 30 pulses as an ultrafast optical data packet over approximately an 80-ps temporal window.

Broadband polarization correction with programmable liquid-crystal modulator arrays.

We demonstrate a novel method of parallel, multiwavelength state-of-polarization (SOP) correction. Using a new liquid-crystal modulator array design, we are able to rotate the distorted input SOP spectrum to a fixed linear state on a wavelength-by-wavelength basis. We report experimental correction of up to 25.5-dB polarization-dependent loss over a 13-nm bandwidth around 1550 nm.

Fast wavelength-parallel polarimeter for broadband optical networks.

We describe a novel wavelength-parallel polarimeter operating in the light-wave band that measures the complete state of polarization of 256 wavelengths in parallel within 20 ms (software-limited), with the potential for submillisecond operation. By use of fast switching ferroelectric liquid crystals in conjunction with an InGaAs arrayed detector, selection and wavelength-parallel detection of individual polarization components can be achieved within approximately 150 microseconds. This instrument offers unprecedented sensing capability that is relevant to the compensation of polarization-related impairments in high-speed light-wave communications.

Direct field-resolved detection of terahertz transients with amplitudes of megavolts per centimeter.

Phase-matched difference-frequency mixing in a thin GaSe crystal within the broad spectrum of 25-fs pulses from a Ti:sapphire oscillator multipass amplifier system permits the generation of few-cycle electric field transients, frequencies up to 30 THz, and amplitudes of more than 1 MV/cm. The field transients generated at a 1-kHz repetition rate are directly measured by electro-optic sampling by 12-f probe pulses from the 75-MHz repetition-rate Ti:sapphire oscillator in combination with a novel electronic gating technique.

Temporal response of a random medium from third-order laser speckle frequency correlations.

We demonstrate for the first time that the temporal response of a random medium can be obtained from optical intensity fluctuations. Our method uses third-order intensity correlations of measured speckle patterns from a multiple scattering random medium as a function of optical frequency. In particular, our experimental results for the temporal response extracted from third-order intensity correlations are in good agreement with the predictions of a diffusion model. Our results are valid for waves in random media where the scattered field is described by circular complex Gaussian statistics.