Aims:  To determine the effects of surface cell concentration and phase of growth on the inactivation of Escherichia coli cells using an atmospheric nonthermal plasma. Methods and Results:  Cells of E. coli K12 were deposited onto the surface of membrane filters and exposed to the plume from a cold atmospheric gas plasma. Scanning electron microscopy revealed severe loss in structural integrity of plasma‐treated cells, and optical emission spectra indicated that inactivation was brought about by reactive plasma species. The survival of E. coli cells was found to depend on the cell surface density: as the surface density increased from 107 to 1011 CFU cm−2, the rate constant in the Baranyi inactivation model decreased from 19·59 to 1·03 min−1. Cells harvested from mid‐exponential, late exponential and stationary phases of growth displayed differences in their resistances to the effects of the plasma however, exponential phase cells were not more susceptible than those from the stationary phase. Conclusions:  High surface concentrations of cells affects the penetration of plasma species and treatment effectiveness. The physiological state of cells, as determined by phase of growth, affects their resistance to plasma inactivation. Significance and Impact of the Study:  In designing inactivation treatments, surface concentration and cell physiology need to be taken into account.

X-ray crystallography is one of the main methods to determine atomic-resolution 3D images of the whole spectrum of molecules ranging from small inorganic clusters to large protein complexes consisting of hundred-thousands of atoms that constitute the macromolecular machinery of life. Life is not static, and unravelling the structure and dynamics of the most important reactions in chemistry and biology is essential to uncover their mechanism. Many of these reactions, including photosynthesis which drives our biosphere, are light induced and occur on ultrafast timescales. These have been studied with high time resolution primarily by optical spectroscopy, enabled by ultrafast laser technology, but they reduce the vast complexity of the process to a few reaction coordinates. In the AXSIS project at CFEL in Hamburg, funded by the European Research Council, we develop the new method of attosecond serial X-ray crystallography and spectroscopy, to give a full description of ultrafast processes atomically resolved in real space and on the electronic energy landscape, from co-measurement of X-ray and optical spectra, and X-ray diffraction. This technique will revolutionize our understanding of structure and function at the atomic and molecular level and thereby unravel fundamental processes in chemistry and biology like energy conversion processes. For that purpose, we develop a compact, fully coherent, THz-driven atto-second X-ray source based on coherent inverse Compton scattering off a free-electron crystal, to outrun radiation damage effects due to the necessary high X-ray irradiance required to acquire diffraction signals. This highly synergistic project starts from a completely clean slate rather than conforming to the specifications of a large free-electron laser (FEL) user facility, to optimize the entire instrumentation towards fundamental measurements of the mechanism of light absorption and excitation energy transfer. A multidisciplinary team formed by laser-, accelerator,- X-ray scientists as well as spectroscopists and biochemists optimizes X-ray pulse parameters, in tandem with sample delivery, crystal size, and advanced X-ray detectors. Ultimately, the new capability, attosecond serial X-ray crystallography and spectroscopy, will be applied to one of the most important problems in structural biology, which is to elucidate the dynamics of light reactions, electron transfer and protein structure in photosynthesis.

Aims:  Escherichia coli and Bacillus subtilis spores were treated with an atmospheric plasma mixture created by the ionization of helium and oxygen to investigate the inactivation efficiency of a low‐temperature plasma below 70°C. Methods and results:  An electrical discharge plasma was produced at a radio frequency (RF) of 13·56 MHz, connected to a perforated circular electrode with a discharge spacing of 1–15 mm. The discharge gas was helium with 0–2% oxygen. For the plasma treatment, a dried E. coli cell or B. subtilis endospore suspension on a cover‐glass was exposed to oxygen downstream of the plasma from holes in an RF‐powered electrode. The sterilization effect of the RF plasma was highest with 0·2% oxygen, corresponding to the maximum production of oxygen radicals. Conclusions:  Oxygen radicals generated by RF plasma are effective for the destruction of bacterial cells and endospores. Significance and Impact of the study:  Low‐temperature atmospheric plasma can be used for the disinfection of diverse objects, especially for the inactivation of bacterial endospores.

He-induced W nanofuzz growth over the W divertor target is one of the main limiting factors affecting the current design and development of fusion reactors. In this paper, based on He reaction rate model in W, we simulate the growth and evolution of He nanobubbles during W nanofuzz formation under fusion-relevant He+ irradiation conditions. Our modeling unveils the existence of He nanobubble-enriched W surface layer (<10 nm), formed due to the He diffusion in W crystal into defect sites. At an elevated temperature, the growth of He bubbles in the W surface layer prevents He atoms diffusing into the deep layer (>10 nm). The formation of W nanofuzz at the surface is attributed to surface bursting of high-density He bubbles with their radius of ~4 nm, and an increase in the surface area of irradiated W. Our findings have been well confirmed by the experimental measurements.

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A large-power inductively coupled plasma source was designed to perform the continuous helium ions (He +) irradiations of polycrystalline tungsten (W) under International Thermonuclear Experimental Reactor (ITER) relevant conditions. He + irradiations were performed at He + fluxes of 2.310 21-1.610 22 /m 2 s and He + energies of 12-220 eV. Surface damages and microstructures of irradiated W were observed by scanning electron microscopy. This study showed the growth of nano-fuzzes with their lengths of 1.3-2.0 m at He + energies of >70 eV or He + fluxes of >1.310 22 /m 2 s. Nanometer-sized defects or columnar microstructures were formed in W surface layer due to low-energy He + irradiations at an elevated temperature (>1300 K). The diffusion and coalescence of He atoms in W surface layers led to the growth and structures of nano-fuzzes. This study indicated that a reduction of He + energy below 12-30 eV may greatly decrease the surface damage of tungsten diverter in the fusion reactor.

Although W fuzz is formed in the divertor region of the fusion reactor, no theory may clearly explain the W fuzz growth mechanism. In this study, we observe the growth process of W fuzz over W crystal under ITER-relevant He ion irradiations. We propose the tensile stress-driven cracking of nano-structured fuzz during the initial growth of W fuzz. We demonstrate that the existence of tensile stress is due to the swelling of He nano-bubbles in the fuzz. After this cracking, the W fuzz breaks away from the planar network and grows over the W surface, where the micro-stress in the W surface layer acts as the driving force.

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