UV and VUV spectroscopy and photochemistry of small molecules in a supersonic jet

UV and VUV absorption and emission spectroscopy is used to probe jet cooled molecules, free radicals, and clusters in the gas phase. Due to efficient cooling inhomogeneous effects on spectral line widths are eliminated. Therefore from these spectra, both structural and dynamical information is obtained. The photoproducts of these reactions are probed by resonance enhanced multiphoton ionization

Widely-tunable mid-IR frequency comb source based on difference frequency generation

We report on a mid-infrared frequency comb source of unprecedented tunability covering the entire 3-10 {\mu}m molecular fingerprint region. The system is based on difference frequency generation in a GaSe crystal pumped by a 151 MHz Yb:fiber frequency comb. The process was seeded with Raman shifted solitons generated in a highly nonlinear suspended-core fiber with the same source. Average powers up to 1.5 mW were achieved at 4.7 {\mu}m wavelength.Comment: 3 pages, 3 figure

Full phase stabilization of a Yb:fiber femtosecond frequency comb via high-bandwidth transducers

We present full phase stabilization of an amplified Yb:fiber femtosecond frequency comb using an intra-cavity electro-optic modulator and an acousto-optic modulator. These transducers provide high servo bandwidths of 580 kHz and 250 kHz for frep and fceo, producing a robust and low phase noise fiber frequency comb. The comb was self-referenced with an f - 2f interferometer and phase locked to an ultra-stable optical reference used for the JILA Sr optical clock at 698 nm, exhibiting 0.21 rad and 0.47 rad of integrated phase errors (over 1 mHz - 1 MHz) respectively. Alternatively, the comb was locked to two optical references at 698 nm and 1064 nm, obtaining 0.43 rad and 0.14 rad of integrated phase errors respectively

Indications for rootstock related ecological preferences of grape phylloxera (Daktulosphaira vitifoliae Fitch)

By parasitizing the roots of Vitis species, grape phylloxera (Daktulosphaira vitifoliae Fitch, Phylloxeridae) is one of the most devastating pests in viticulture. Grafting susceptible scions (Vitis vinifera) to tolerant Vitis rootstocks is a common practice to control grape phylloxera in wine growing regions worldwide. However, grape phylloxera populations still develop on the roots of most grafting combinations. Questions remain as to whether or not the impact of environmental factors on grape phylloxera population dynamics is related to Vitis rootstock cultivars. In the presented field study, we investigated the influence of two closely related mature Vitis berlandieri x Vitis riparia rootstock varieties on the relations between the dynamics of root feeding grape phylloxera populations, root morphology and abiotic factors. The investigation took place on a commercial vineyard in Geisenheim/Germany on Teleki 5C/V. vinifera 'Weisser Riesling' and Kober 125AA/V. vinifera 'Weisser Riesling'. Samples of roots, attached grape phylloxera populations and soil were taken in the field 19 times between August 2007 and August 2009. Grape phylloxera population structure was recorded by the occurrence of root-feeding wingless females, fundatrices and nymphs and the pigmentation and position of root galls were assessed. Root morphological parameters were assessed using WinRhizo Pro. Soil abiotic parameters were assessed in the laboratory. Results of a principal component analysis showed rootstock related differences considering the impact of abiotic factors on grape phylloxera population structure. Especially soil temperature and soil organic matter were indicated to have a lower impact on grape phylloxera population structure on roots of 5C than on roots of 125AA. Our data indicate that ecological factors have a lower impact on the development of grape phylloxera on more supportive rootstocks

Forecasting Proximal Femur and Wrist Fracture Caused by a Fall to the Side during Space Exploration Missions to the Moon and Mars

The possibility of bone fracture in space is a concern due to the negative impact it could have on a mission. The Bone Fracture Risk Module (BFxRM) developed at the NASA Glenn Research Center is a statistical simulation that quantifies the probability of bone fracture at specific skeletal locations for particular activities or events during space exploration missions. This paper reports fracture probability predictions for the proximal femur and wrist resulting from a fall to the side during an extravehicular activity (EVA) on specific days of lunar and Martian exploration missions. The risk of fracture at the proximal femur on any given day of the mission is small and fairly constant, although it is slightly greater towards the end of the mission, due to a reduction in proximal femur bone mineral density (BMD). The risk of wrist fracture is greater than the risk of hip fracture and there is an increased risk on Mars since it has a higher gravitational environment than the moon. The BFxRM can be used to help manage the risk of bone fracture in space as an engineering tool that is used during mission operation and resource planning

Broadband Phase-Noise Suppression in a Yb-Fiber Frequency Comb

We report a simple technique to suppress high frequency phase noise of a Yb-based fiber optical frequency comb using an active intensity noise servo. Out-of-loop measurements of the phase noise using an optical heterodyne beat with a continuous wave (cw) laser show suppression of phase noise by \geq7 dB out to Fourier frequencies of 100 kHz with a unity-gain crossing of -700 kHz. These results are enabled by the strong correlation between the intensity and phase noise of the laser. Detailed measurements of intensity and phase noise spectra, as well as transfer functions, reveal that the dominant phase and intensity noise contribution above -100 kHz is due to amplified spontaneous emission (ASE) or other quantum noise sources.Comment: 4 pages, 3 figure

Computational modelling and experimental tank testing of the multi float WaveSub under regular wave forcing

A submerged wave device generates energy from the relative motion of floating bodies. In WaveSub, three floats are joined to a reactor; each connected to a spring and generator. Electricity generated damps the orbital movements of the floats. The forces are non-linear and each float interacts with the others. Tuning to the wave climate is achieved by changing the line lengths, so there is a need to understand the performance trade-offs for a large number of configurations. This requires an efficient, large displacement, multidirectional, multi-body numerical scheme. Results from a 1/25 scale wave basin experiment are described. Here, we show that a time domain linear potential flow formulation (Nemoh, WEC-Sim) can match the tank testing provided that suitably tuned drag coefficients are employed. Inviscid linear potential models can match some wave device experiments; however, additional viscous terms generally provide better accuracy. Scale experiments are also prone to mechanical friction, and we estimate friction terms to improve the correlation further. The resulting error in mean power between numerical and physical models is approximately 10%. Predicted device movement shows a good match. Overall, drag terms in time domain wave energy modelling will improve simulation accuracy in wave renewable energy device design

Computational modelling and experimental tank testing of the multi float WaveSub under regular wave forcing

A submerged wave device generates energy from the relative motion of floating bodies. In 1 WaveSub, three floats are joined to a reactor; each connected to a spring and generator. Electricity generated 2 damps the orbital movements of the floats. The forces are non-linear and each float interacts with the others. 3 Tuning to the wave climate is achieved by changing the line lengths so there is a need to understand the 4 performance trade-offs for a large number of configurations. This requires an efficient, large displacement, 5 multidirectional, multi-body numerical scheme. Results from a 1/25 scale wave basin experiment are described. 6 Here we show that a time domain linear potential flow formulation (Nemoh, WEC-Sim) can match the tank 7 testing provided that suitably tuned drag coefficients are employed. Inviscid linear potential models can match 8 some wave device experiments, however, additional viscous terms generally provide better accuracy. Scale 9 experiments are also prone to mechanical friction and we estimate friction terms to improve the correlation 10 further. The resulting error in mean power between numerical and physical models is approximately 10%. 11 Predicted device movement shows a good match. Overall, drag terms in time domain wave energy modelling 12 will improve simulation accuracy in wave renewable energy device design