Green-pumped, picosecond MgO:PPLN optical parametric oscillator

We investigate the performance of a magnesium-oxide-doped periodically poled lithium niobate crystal (MgO:PPLN) in an optical parametric oscillator (OPO) synchronously-pumped by 530nm, 20ps, 230MHz pulses with an average power of up to 2W from a frequency-doubled, gain-switched laser diode seed and a multi-stage Yb:fiber amplifier system. The OPO produces ~165mW (signal, 845nm) and ~107mW (idler, 1421nm) of average power for ~1W of pump power and can be tuned from ~800nm to 900nm (signal) and 1.28µm to 1.54µm (idler). Observations of photo-refraction and green-induced infrared absorption (GRIIRA) in different operational regimes of the MgO:PPLN OPO are described and the role of peak intensity and average power are investigated, both with the aim to find the optimal operating regime for pulsed systems

CoCStom trial: study protocol for a randomised trial comparing completeness of adjuvant chemotherapy after early versus late diverting stoma closure in low anterior resection for rectal cancer

Background: Current evidence supports a diverting stoma in patients undergoing low anterior resection with total mesorectal excision for rectal cancer as it reduces clinical severity of anastomotic leakage. However, relevant stoma morbidity after rectal cancer surgery exists and has a significant impact on quality of life. Moreover, a diverting stoma has an influence on completeness of chemotherapy but it remains unclear in which way. There is no evidence regarding optimal timing for stoma closure in relation to adjuvant chemotherapy. Two randomised controlled trials have studied early stoma closure after low anterior resection in patients with rectal cancer, one of them showing that early closure around day 8 after resection is possible without increasing morbidity. Methods/Design: CoCStom is a randomised multicentre trial comparing completeness of adjuvant chemotherapy as primary endpoint after early (8–10 days after resection, before starting adjuvant therapy) versus late (~26 weeks after resection and completion of adjuvant therapy) stoma closure in patients with locally advanced rectal cancer undergoing low anterior resection after neoadjuvant therapy. After exclusion of post-operative anastomotic leakage 257 patients from 30 German hospitals are planned to be included in order to assure a power of 80 % for the confirmatory analysis of at least 214 evaluable cases. An absolute increase of 20 % for the rate of completely administered adjuvant chemotherapy is regarded as a clinically meaningful step forward and serves as basis for sample size calculation. Quality of life, stoma-related complications, individual completeness of chemotherapy rate, percentage of patients stopping adjuvant therapy or undergoing dose modifications or delay, oncological outcomes, cumulative days of hospitalisation and number of readmissions, rate of symptomatic anastomotic leaks after stoma closure, mortality, post-operative complications and toxicity of adjuvant chemotherapy are secondary endpoints. Discussion: The CoCStom trial aims to clarify optimal timing of stoma closure in the context of adjuvant chemotherapy. Depending on the results of the trial, patients could benefit either from early or late stoma closure in regard to long term oncological survival due to a higher rate of completeness of adjuvant chemotherapy treatment and thus better effectiveness. Trial registration: German Clinical Trials Register, DRKS00005113 . Registered 28 August 201

A picosecond optical parametric oscillator synchronously pumped by an amplified gain-switched laser diode

We demonstrate a picosecond optical parametric oscillator synchronously pumped by a fiber-amplified gain-switched laser diode. Up to 7.3W at 1.54µm and 3.1W at 3.4µm is obtained at pulse repetition rates between 114.8 and 918.4MHz

Wet-Chemical Assembly of 2D Nanomaterials into Lightweight, Microtube-Shaped, and Macroscopic 3D Networks

Despite tremendous efforts toward fabrication of three-dimensional macrostructures of two-dimensional (2D) materials, the existing approaches still lack sufficient control over microscopic (morphology, porosity, pore size) and macroscopic (shape, size) properties of the resulting structures. In this work, a facile fabrication method for the wet-chemical assembly of carbon 2D nanomaterials into macroscopic networks of interconnected, hollow microtubes is introduced. As demonstrated for electrochemically exfoliated graphene, graphene oxide, and reduced graphene oxide, the approach allows for the preparation of highly porous (> 99.9%) and lightweight (<2 mg cm-3) aeromaterials with tailored porosity and pore size as well as tailorable shape and size. The unique tubelike morphology with high aspect ratio enables ultralow-percolation-threshold graphene composites (0.03 S m-1, 0.05 vol%) which even outperform most of the carbon nanotube-based composites, as well as highly conductive aeronetworks (8 S m-1, 4 mg cm-3). On top of that, long-term compression cycling of the aeronetworks demonstrates remarkable mechanical stability over 10 000 cycles, even though no chemical cross-linking is employed. The developed strategy could pave the way for fabrication of various macrostructures of 2D nanomaterials with defined shape, size, as well as micro- and nanostructure, crucial for numerous applications such as batteries, supercapacitors, and filters

In-vivo multilaboratory investigation of the optical properties of the human head

The in-vivo optical properties of the human head are investigated in the 600–1100 nm range on different subjects using continuous wave and time domain diffuse optical spectroscopy. The work was performed in collaboration with different research groups and the different techniques were applied to the same subject. Data analysis was carried out using homogeneous and layered models and final results were also confirmed by Monte Carlo simulations. The depth sensitivity of each technique was investigated and related to the probed region of the cerebral tissue. This work, based on different validated instruments, is a contribution to fill the existing gap between the present knowledge and the actual in-vivo values of the head optical properties

Health Care Workers’ Sick Leave due to COVID-19 Vaccination in Context With SARS-CoV-2 Infection and Quarantine—A Multicenter Cross-Sectional Survey

Background Reactogenicity of coronavirus disease 2019 (COVID-19) vaccines can result in inability to work. The object of this study was to evaluate health care workers’ sick leave after COVID-19 vaccination and to compare it with sick leave due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and quarantine leave. Methods A multicenter cross-sectional survey was conducted at Regensburg University Medical Center and 10 teaching hospitals in South-East Germany from July 28 to October 15, 2021. Results Of 2662 participants, 2309 (91.8%) were fully vaccinated without a history of SARS-CoV-2 infection. Sick leave after first/second vaccination occurred in 239 (10.4%) and 539 (23.3%) participants. In multivariable logistic regression, the adjusted odds ratio for sick leave after first/second vaccination compared with BNT162b2 was 2.26/3.72 for mRNA-1237 (95% CI, 1.28–4.01/1.99–6.96) and 27.82/0.48 for ChAdOx1-S (95% CI, 19.12–40.48/0.24–0.96). The actual median sick leave (interquartile range [IQR]) was 1 (0–2) day after any vaccination. Two hundred fifty-one participants (9.4%) reported a history of SARS-CoV-2 infection (median sick leave [IQR] 14 [10–21] days), 353 (13.3%) were quarantined at least once (median quarantine leave [IQR], 14 [10–14] days). Sick leave due to SARS-CoV-2 infection (4642 days) and quarantine leave (4710 days) accounted for 7.7 times more loss of workforce than actual sick leave after first and second vaccination (1216 days) in all fully vaccinated participants. Conclusions Sick leave after COVID-19 vaccination is frequent and is associated with the vaccine applied. COVID-19 vaccination should reduce the much higher proportion of loss of workforce due to SARS-CoV-2 infection and quarantine

QCD and strongly coupled gauge theories : challenges and perspectives

We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Peer reviewe

Advanced high-power optical parametric oscillators synchronously pumped by ultrafast fibre-based sources

This thesis is concerned with investigating the generation of ultra short, tunable pulses at high average power and / or high pulse energy using synchronously pumped optical parametric oscillators (OPO) and appropriate power-scalable fibre-amplifier pump sources. Two types of pump sources with average powers up to ~100W are considered: (1) a picosecond, all-fiberised, high-power, variable-repetition-rate, Yb:fibre-amplified, gain-switched laser diode system and (2) a femtosecond, high-power, chirped-pulse amplification Yb:fibre laser system incorporating a pulse shaper module. Such OPO systems find applications in fields as diverse as materials processing and nonlinear microscopy / spectroscopy. Two OPOs based on periodically poled lithium niobate (PPLN) and pumped at 1060nm from the first pump source are demonstrated. With 20ps-long pump pulses, average powers of up to 7.3W (3.1W) for the signal (idler) are generated at variable repetition rates of ~0.1 . . . 1GHz. With longer 100ps pump pulses at a repetition rate of &lt; 8MHz and an intracavity fibre as an OPO feedback component for compactness, combined pulse energies approaching 1µJ are obtained, which are the highest reported to date. Tuning ranges from 1.4µm to 1.7µm (signal) and from 2.8µm to 4.4µm (idler) are typical for both OPOs. Including frequency-doubling of the 1060 nm light, the first pump source, operating at 230MHz and 20ps, is used for two green-pumped OPOs tunable in the near-infrared range from 650 nm to 1040nm (plus the idler from 1.08µm to 2.9µm). The first OPO uses MgO-doped PPLN and up to 270mW of combined output power with 1W of pump power is obtained. Operation at higher power is complicated due to damage effects such as photo-refraction, nonlinear or induced absorption in lithium niobate. The second OPO uses lithium triborate (LBO) and compressed 4.4ps green pump pulses to generate record average powers of up to 3.7W of signal and 1.8W of idler. Using the second pump source with a liquid crystal spatial light modulator pulse shaper, the demonstration of energy-scalable output pulses from 0.1µJ to 2µJ at a centre wavelength of 1045nm with typical pulse durations between 300fs and 600fs is reported. Pump pulses with a duration of ~ 600 fs at a repetition rate of 50MHz from this pump source are used for a PPLN OPO producing ~ 1.9W (~ 1.2W) of signal (idler) power at 1.5µm (3.6µm)