Droplet streams for serial crystallography of proteins

Serial diffraction of proteins requires an injection method to deliver protein molecules - preferably uncharged, fully hydrated, spatially oriented, and with high flux - into the crossed beams of an alignment laser and a focused probe beam of electrons or X-rays of typically only a few tens of microns diameter. The aim of this work has been to examine several potential droplet sources as to their suitability for this task. We compare Rayleigh droplet sources, electrospray sources, nebulizers and aerojet-focused droplet sources using time-resolved optical images of the droplet beams. Shrinkage of droplets by evaporation as a means of removing most of the water surrounding the proteins is discussed. Experimental measurements of droplet size, conformation of proteins after passing through a Rayleigh jet, and triboelectric charging are presented and conclusions are drawn about the source configuration for serial diffraction. First experimental X-ray diffraction patterns from Rayleigh droplet beams doped with 100nm gold balls are shown.Comment: 29 page

Ecosystem responses to warming and watering in typical and desert steppes

Global warming is projected to continue, leading to intense fluctuations in precipitation and heat waves and thereby affecting the productivity and the relevant biological processes of grassland ecosystems. Here, we determined the functional responses to warming and altered precipitation in both typical and desert steppes. The results showed that watering markedly increased the aboveground net primary productivity (ANPP) in a typical steppe during a drier year and in a desert steppe over two years, whereas warming manipulation had no significant effect. The soil microbial biomass carbon (MBC) and the soil respiration (SR) were increased by watering in both steppes, but the SR was significantly decreased by warming in the desert steppe only. The inorganic nitrogen components varied irregularly, with generally lower levels in the desert steppe. The belowground traits of soil total organic carbon (TOC) and the MBC were more closely associated with the ANPP in the desert than in the typical steppes. The results showed that the desert steppe with lower productivity may respond strongly to precipitation changes, particularly with warming, highlighting the positive effect of adding water with warming. Our study implies that the habitat- and year-specific responses to warming and watering should be considered when predicting an ecosystem’s functional responses under climate change scenarios

Assessing written work by determining competence to achieve the module-specific learning outcomes.

This chapter describes lasers and other sources of coherent light that operate in a wide wavelength range. First, the general principles for the generation of coherent continuous-wave and pulsed radiation are treated including the interaction of radiation with matter, the properties of optical resonators and their modes as well as such processes as Q-switching and mode-locking. The general introduction is followed by sections on numerous types of lasers, the emphasis being on todayʼs most important sources of coherent light, in particular on solid-state lasers and several types of gas lasers. An important part of the chapter is devoted to the generation of coherent radiation by nonlinear processes with optical parametric oscillators, difference- and sum-frequency generation, and high-order harmonics. Radiation in the extended ultraviolet (EUV) and x-ray ranges can be generated by free electron lasers (FEL) and advanced x-ray sources. Ultrahigh light intensities up to 1021 W/cm2 open the door to studies of relativistic laser–matter interaction and laser particle acceleration. The chapter closes with a section on laser stabilization