https://www.biorxiv.org/content/biorxiv/early/2020/02/20/2020.02.19.956581.full.pdf

Structure, Function, and Antigenicity of the SARS-CoV-2 Spike Glycoprotein.

Recent research on fibre optic long-period gratings (LPGs) is reviewed with emphasis placed upon the characteristics of LPGs that make them attractive for applications in sensing strain, temperature, bend radius and external index of refraction. The prospect of the development of multi-parameter sensors, capable of simultaneously monitoring a number of these measurands will be discussed.

https://iopscience.iop.org/article/10.1088/0957-0233/14/5/201/pdf

Optical fibre long-period grating sensors: characteristics and application

Comprehensive mapping of mutations in the SARS-CoV-2 receptor-binding domain that affect recognition by polyclonal human plasma antibodies.

Complete Mapping of Mutations to the SARS-CoV-2 Spike Receptor-Binding Domain that Escape Antibody Recognition.

Journal of Scientific Instruments Editor: Dr H R Lang Vol 28 and Supplement No 1, 1951 Pp xvi + 388 + iii + 80 (London: Institute of Physics, 1951) Bound, £3 12s; unbound, £3

/pdf/a-review-of-scientific-instruments-50cfd4j98s.pdf

A Review of Scientific Instruments

https://www.physics.utoronto.ca/~marj/references/Herman2000-9.pdf

Laser shaping of photonic materials: deep-ultraviolet and ultrafast lasers

This study reports on the multi-pulse ablation of aluminum foils by bursts of mode-locked pulses from a feedback-controlled Nd:glass laser (1054 nm). The 2-μs train consists of about 250 pulses of 1.2 ps duration and 7.5 ns pulse-to-pulse separation. The bursts provide a new mode of laser fluence delivery, combining long-pulse heating with the advantages of ultrashort laser material interactions. Results show that clean through-holes can be cut through 200-μm foils with a single pulse train. In holes produced using near-threshold machining, a 7:1 aspect ratio was observed with a taper half-angle of around 3°. The etch depths and surface morphology of the processed surfaces are qualitatively characterized for fluences between 80 J/cm2 and 9 kJ/cm2, and for a range of foil thicknesses 12.5–200 μm.

Ultra high repetition rate (133 MHz) laser ablation of aluminum with 1.2-ps pulses

Ablation rates and etched-surface morphology of fused silica has been studied with 1-ps Nd:glass laser pulses in a regime of near-diffraction-limited spot size. Shallow holes of 1.7- micrometers diameter were too small for the formation of laser- induced periodic-surface structures. Atomic-force and scanning-electron microscopy showed that reproducible etch depth and moderately smooth surfaces are attainable for low fluences of 5.5 - 45 J/cm2--the `gentle' ablation regime. Etch depth progressed linearly with the number of laser pulses until the onset of surface swelling and shock- induced microcracks after a critical number Nc of laser pulses, scaling as Nc equals 1.7 + 80/F (fluence F in J/cm2). Below this limit--for accumulated etch depths less than approximately 2 micrometers --3D surface structuring with sub-micron precision is possible with picosecond-laser pulses. In the strong ablation regime (F > 45 J/cm2), surface morphology was poor and microcracking developed within 2 - 4 pulses. These shock-induced microcracking effects were eliminated when a mode-locked train of approximately 400 identical 1-ps pulses, each separated by 7.5 ns, was applied. Very smooth and deep (approximately 30- micrometers ) holes of 7 - 10-micrometers diameter were excised at a total fluence of approximately 100 kJ/cm2, establishing a new means for rapid and precise micromachining of fused silica and other brittle materials.

Laser micromachining of transparent fused silica with 1-ps pulses and pulse trains

RNA viruses are characterized by a high mutation rate, a buffer against environmental change. Nevertheless, the means by which random mutation improves viral fitness is not well characterized. Here we report the X-ray crystal structure of the receptor-binding domain (RBD) of the human coronavirus, HCoV-229E, in complex with the ectodomain of its receptor, aminopeptidase N (APN). Three extended loops are solely responsible for receptor binding and the evolution of HCoV-229E and its close relatives is accompanied by changing loop-receptor interactions. Phylogenetic analysis shows that the natural HCoV-229E receptor-binding loop variation observed defines six RBD classes whose viruses have successively replaced each other in the human population over the past 50 years. These RBD classes differ in their affinity for APN and their ability to bind an HCoV-229E neutralizing antibody. Together, our results provide a model for alphacoronavirus adaptation and evolution based on the use of extended loops for receptor binding.

/pdf/receptor-binding-loops-in-alphacoronavirus-adaptation-and-miu4zi4jqk.pdf

Receptor-binding loops in alphacoronavirus adaptation and evolution.

Long-period gratings were fabricated in standard telecommunication fiber (Corning SMF-28) by use of what is believed to be record short-wavelength light from a 157-nm F2 laser. Strong loss peaks were formed without the need for enhancement techniques such as hydrogen loading. The magnitude of the attenuation peak was sensitive to the single-pulse laser fluence, decreasing with increasing pulse fluence as a result of nonuniform 157-nm laser interaction with both the fiber cladding and core. The long-period fiber gratings have good wavelength stability Δλ∼7 nm under thermal annealing at 150 °C.

/pdf/fabrication-of-strong-long-period-gratings-in-hydrogen-free-o1lxpfwkvu.pdf

Kevin P. Chen

Papers

Laser shaping of photonic materials: deep-ultraviolet and ultrafast lasers

Ultra high repetition rate (133 MHz) laser ablation of aluminum with 1.2-ps pulses

Laser micromachining of transparent fused silica with 1-ps pulses and pulse trains

Receptor-binding loops in alphacoronavirus adaptation and evolution.

Fabrication of strong long-period gratings in hydrogen-free fibers with 157-nm F 2 -laser radiation