Femtosecond photoelectron and photoion spectrometer with vacuum ultraviolet probe pulses

We describe a setup to study ultrafast dynamics in gas-phase molecules using time-resolved photoelectron and photoion spectroscopy. The vacuum ultraviolet (VUV) probe pulses are generated via strong field high-order harmonic generation from infrared femtosecond laser pulses. The band pass characteristic in transmission of thin indium (In) metal foil is exploited to isolate the $9^{\text{th}}$ harmonic of the 800 nm fundamental (H9, 14 eV, 89 nm) from all other high harmonics. The $9^{\text{th}}$ harmonic is obtained with high conversion efficiencies and has sufficient photon energy to access the complete set of valence electron levels in most molecules. The setup also allows for direct comparison of VUV single-photon probe with 800 nm multi-photon probe without influencing the delay of excitation and probe pulse or the beam geometry. We use a magnetic bottle spectrometer with high collection efficiency for electrons, serving at the same time as a time of flight spectrometer for ions. Characterization measurements on Xe reveal the spectral width of H9 to be $190\pm60$ meV and a photon flux of $\sim1\cdot10^{7}$ photons/pulse after spectral filtering. As a first application, we investigate the S$_1$ excitation of perylene using time-resolved ion spectra obtained with multi-photon probing and time-resolved electron spectra from VUV single-photon probing. The time resolution extracted from cross-correlation measurements is $65\pm10$ fs for both probing schemes and the pulse duration of H9 is found to be $35\pm8$ fs

Spectral analysis of residual GRACE and GRACE-FO range accelerations

GRACE and GRACE-FO K-band range-rate post-fit residuals obtained after a common estimation of monthly gravity field coefficients and ancillary satellite parameters represent a complex superposition of different effects. In this contribution, we analyze the component of the residuals that is related to geophysical effects. We low pass filter and differentiate range-rate post-fit residuals to obtain residual range-accelerations. A spectral analysis of globaly gridded residual range-accelerations reveals unmodeled signal related to (ocean) tides and hydrology. The time series with approximately 100 millions of data records allows us to identify main periodic contributors in different bands. Diurnal and semi-diurnal signal can be resolved on a 5x5 degree grid, while periods of 5 and 3 hours can be resolved on a 7.5x7.5 and 10x10 degree grid

Influence of accelerometer parametrizations on GRACE post-fit residuals

Accelerometers onboard of satellites can be regarded as a key improvement in gravity field recovery. These instruments are located in the center of mass of the satellite and are precisely measuring non-gravitational forces acting on the satellite surfaces. Accelerometer measurements are distorted in their magnitude and amplitude, so an accelerometer calibration has to be carried out. Usually, in orbit determination and gravity field parameter estimation, a priori values are introduced and corresponding numeric corrections are estimated iteratively. Within the gravity field recovery community various accelerometer calibration parametrizations are applied. We have tested several parametrization scenarios within our in-house developed GRACE-SIGMA gravity field recovery software. In this contribution, we present the impact of these scenarios on post- fit KBRR residuals

Residual ocean tide signal in GRACE(-FO) range-rate post-fit residuals

Ocean tide model imperfections are one of the major uncertainty factors in gravity field recovery. Unmodeled signal can alias into level-2 gravity field products and be interpreted as real signal, e.g. as ice mass loss. An accurate understanding of the ocean tide model imperfections (on spectral and spatial level) is therefore not only important for current, but also for future gravity field missions. For this contribution, we analyzed 20+ years of GRACE(-FO) K-band range-rate post-fit residuals for residual ocean tide signal. The post-fit residuals are obtained as part of the gravity field estimation of monthly solutions. We low pass filter and differentiate range-rate post-fit residuals to obtain residual range-accelerations. Obtained residual range-accelerations are assigned to 5x5 degree grid cells and Lomb-Scargle periodograms for each cell are computed. An analysis of the periodograms reveals peaks at frequencies of ocean tide constituents. The peaks with the largest spectral amplitude can be found at frequencies of the major constituents (O1, M2, K1). In total around 30 constituents are detectable, among them also compound tides and degree-3 tides

GRACE-FO monthly solutions using the GRACE-SIGMA software

In this contribution we present gravity field monthly solutions from GRACE Follow-On (GRACE-FO) Level-1B sensor data. The monthly solutions are computed with the GRACE-SIGMA software developed at the Institute of Geodesy, Leibniz University Hannover. The solutions are obtained using a two-step approach. In a first step, the orbits of the two satellites are pre-adjusted by estimating local arc parameters. In a second step, the monthly gravity field potential in terms of normalized spherical harmonic coefficients is recovered. Several parametrization scenarios are tested and the obtained solutions are compared with solutions of other processing centers. Furthermore, K-band range-rate (KBRR) post-fit residuals are analyzed in time, frequency and space domain and are compared to the typical post-fit residuals of the GRACE mission

A new enzymatic route for production of long 5'-phosphorylated oligonucleotides using suicide cassettes and rolling circle DNA synthesis

<p>Abstract</p> <p>Background</p> <p>The quality of chemically synthesized oligonucleotides falls with the length of the oligonucleotide, not least due to depurinations and premature termination during production. This limits the use of long oligonucleotides in assays where long high-quality oligonucleotides are needed (e.g. padlock probes). Another problem with chemically synthesized oligonucleotides is that secondary structures contained within an oligonucleotide reduce the efficiency of HPLC and/or PAGE purification. Additionally, ligation of chemically synthesized oligonucleotides is less efficient than the ligation of enzymatically produced DNA molecules.</p> <p>Results</p> <p>Chemically synthesized oligonucleotides with hairpin structures were acquired from our standard supplier. The stem of the hairpin contained recognition sequences for the Nt. Alw I nicking enzyme and the Mly I restriction enzyme. These double stranded regions were positioned in a way to allow self-templated circularization of the oligonucleotide. Following ligation, tandem repeats of the complementary sequence of the circular oligonucleotide could be produced through rolling circle DNA synthesis. By running successive rounds of ligation, rolling circle DNA synthesis, and nicking, the original oligonucleotide could be amplified as either the (+)-strand or the (-)-strand. Alternatively, the hairpin structure could be removed by cleavage with the Mly I restriction enzyme, thereby releasing the oligonucleotide sequence contained within the hairpin structure from the hairpin.</p> <p>Conclusion</p> <p>We present here a method for the enzymatic production through DNA amplification of oligonucleotides with freely designable 5'-ends and 3'-ends, using hairpin-containing self-templating oligonucleotides. The hairpin comprises recognition sequences for a nicking enzyme and a restriction enzyme. The oligonucleotides are amplified by successive rounds of ligation, rolling circle DNA synthesis and nicking. Furthermore, the hairpin can be removed by cleavage with the Mly I restriction enzyme. We have named such hairpin structures "suicide cassettes".</p

GRACE and GRACE-FO processing at IfE/LUH

Updates on gravity field recovery from GRACE and GRACE Follow-On data at IfE/LUH

GRACE-FO processing at IfE/LUH

Processing strategy of the LUH-GRACE-FO-2020 monthly gravity field time series is presented. The spectral noise, spatial noise and signal content of the time series (2018-06 - 2020-08) is evaluated

Signals of Geophysical Nature in GRACE and GRACE-FO Post-Fit Range-Rate Residuals

Post-fit residuals of satellite-to-satellite tracking measurements of the GRACE and GRACE-FO missions obtained after a common estimation of orbit and gravity field parameters should ideally contain measurement noise with a behavior that meets expectations for the involved sensors. In reality, obtained GRACE and GRACE-FO post-fit range-rate residuals represent a complex superposition of different effects, e.g. of instrumental, environmental and geophysical nature. In this contribution, we focus on the geophysical signals in the post-fit residuals of the LUH GRACE and GRACE-FO time series. We apply band-pass filtering to extract the geophysical signal buried in the residuals and analyze the most distinctive signatures for their spatial and temporal behavior