Generation and measurement of isolated attosecond pulses with enhanced flux using a two colour synthesized laser field.

We have generated isolated attosecond pulses and performed attosecond streaking measurements using a two-colour synthesized laser field consisting of a strong near-infrared few-cycle pulse and a weaker multi-cycle pulse centred at 400 nm. An actively stabilized interferometer was used to coherently combine the two pulses. Using attosecond streaking we characterised the electric fields of the two pulses and accurately retrieved the spectrum of the multi-cycle pulse. We demonstrated a two-fold increase in the flux of isolated attosecond pulses produced and show that their duration was minimally affected by the presence of the weaker field due to spectral filtering by a multilayer mirror.

Exosomes and soluble secretome from hormone-treated endometrial epithelial cells direct embryo implantation.

A successful pregnancy requires a synchronous dialogue between endometrium and embryo within the endometrial milieu. The aim of this study was to assess the role in the implantation of mediators in the endometrial milieu. Total secretome (TS), soluble secretome (SS) and small extracellular vesicles (containing exosomes) were generated from hormonally primed human endometrial epithelial cell culture medium. Human trophectoderm stem cell-derived spheroids were cultured with TS, SS or exosomes (30 µg/ml) on hormonally primed epithelial cells, with exosomes significantly increasing cell adhesion and outgrowth. Furthermore, F1 mouse 2-cell embryos were cultured in groups for 48 h followed by culture with each secretome fraction (30 µg/ml) for 48 h. Blastocyst cell number and hatching were quantified. In addition, blastocysts were further cultured on a fibronectin matrix for 72 h or transferred to recipient mice (with corresponding secretomes) with embryo implantation assessed after 6 days. Exosomes significantly increased total cell number in mouse embryos and complete hatching from zona pellucida, with both exosomes and SS significantly enhancing mouse embryo outgrowth. Importantly, exosomes increased the embryo implantation rate in comparison to other secretome fractions (normalized based on treatment amount) from the endometrial epithelia. These data indicate that endometrial epithelial exosomes support embryo growth, development and implantation while the SS has selective involvement specifically on mouse embryo outgrowth. This finding provides new insights into the molecular differences of endometrial secretome components in implantation and early embryo development and may implicate endometrial exosomes in the pathophysiology of implantation failure in infertility.

Investigation of valence band reconstruction methods for attosecond streaking data from surfaces.

We analyze simulated streaked valence band photoemission with atomic streaking theory-based reconstruction methods to investigate the differences between atomic gas-phase streaking and valence band surface streaking. The careful distinction between atomic and surface streaking is a prerequisite to justify the application of atomic streaking theory-based reconstruction methods to surface streaking measurements. We show that neglecting the band structure underestimates the width of reconstructed photoelectron wavepackets, consistent with the Fourier transform limit of the band spectrum. We find that a fit of Gaussian wavepackets within the description of atomic streaking is adequate to a limited extent. Systematic errors that depend on the near-infrared skin depth, an inherently surface-specific property, are present in temporal widths of wavepackets reconstructed with atomic streaking theory-based methods.

S-nitrosylation and S-glutathionylation of Cys134 on troponin I have opposing competitive actions on Ca2+ sensitivity in rat fast-twitch muscle fibers.

Nitric oxide is generated in skeletal muscle with activity and decreases Ca2+ sensitivity of the contractile apparatus, putatively by S-nitrosylation of an unidentified protein. We investigated the mechanistic basis of this effect and its relationship to the oxidation-induced increase in Ca2+ sensitivity in mammalian fast-twitch (FT) fibers mediated by S-glutathionylation of Cys134 on fast troponin I (TnIf). Force-[Ca2+] characteristics of the contractile apparatus in mechanically skinned fibers were assessed by direct activation with heavily Ca2+-buffered solutions. Treatment with S-nitrosylating agents, S-nitrosoglutathione (GSNO) or S-nitroso-N-acetyl-penicillamine (SNAP), decreased pCa50 ( = -log10 [Ca2+] at half-maximal activation) by ~-0.07 pCa units in rat and human FT fibers without affecting maximum force, but had no effect on rat and human slow-twitch fibers or toad or chicken FT fibers, which all lack Cys134. The Ca2+ sensitivity decrease was 1) fully reversed with dithiothreitol or reduced glutathione, 2) at least partially reversed with ascorbate, indicative of involvement of S-nitrosylation, and 3) irreversibly blocked by low concentration of the alkylating agent, N-ethylmaleimide (NEM). The biotin-switch assay showed that both GSNO and SNAP treatments caused S-nitrosylation of TnIfS-glutathionylation pretreatment blocked the effects of S-nitrosylation on Ca2+ sensitivity, and vice-versa. S-nitrosylation pretreatment prevented NEM from irreversibly blocking S-glutathionylation of TnIf and its effects on Ca2+ sensitivity, and likewise S-glutathionylation pretreatment prevented NEM block of S-nitrosylation. Following substitution of TnIf into rat slow-twitch fibers, S-nitrosylation treatment caused decreased Ca2+ sensitivity. These findings demonstrate that S-nitrosylation and S-glutathionylation exert opposing effects on Ca2+ sensitivity in mammalian FT muscle fibers, mediated by competitive actions on Cys134 of TnIf.

Time-domain ptychography of over-octave-spanning laser pulses in the single-cycle regime.

We report, to the best of our knowledge, the first application of time-domain ptychography for the characterization of few-cycle laser pulses. Our method enables zero-additional phase measurements of over-octave-spanning laser pulses in the single cycle regime. The spectral phase is recovered using a robust ptychography algorithm that requires no input apart from the measured data trace. In addition to numerical tests, we validate our new device experimentally by reconstructing the complex electric field of a 1.5 cycle laser pulse with a bandwidth spanning 490 to 1060 nm. We further check the accuracy of our device by comparing the measured phases of octave-spanning chirped pulses to the known dispersion of fused silica glass.

Self-referenced characterization of space-time couplings in near-single-cycle laser pulses.

We report on the characterization of space-time couplings in high-energy sub-2-cycle 770 nm laser pulses using a self-referencing single-frame method. Using spatially encoded arrangement filter-based spectral phase interferometry for direct electric field reconstruction, we characterize few-cycle pulses with a wavefront rotation of 2.8×1011 rev/s (1.38 mrad per half-cycle) and pulses with pulse front tilts ranging from -0.33 fs/µm to -3.03 fs/µm in the focus.