Harmonic Generation in a Terawatt X-Ray Free-Electron Laser

Terawatt x-ray free-electron lasers (XFELs) require high current densities with strong transverse focusing. The implications on harmonic generation are discussed using the MINERVA simulation code which self-consistently includes harmonic generation. We consider helical and planar undulators where the fundamental is at 1.5 Angstrom and study the associated harmonic generation. While tapered undulators are needed to reach TW powers at the fundamental, the taper does not enhance the harmonics because the taper must start before saturation of the fundamental, with the harmonics saturating earlier. Nevertheless, the harmonics reach substantial powers and enable enhanced applications.Comment: 4 pages, 4 figure

Factors affecting the creaming of human milk

The creaming properties of human milk have not been widely studied to date, and a mechanism for this phenomenon is not known. Here, the natural creaming of human milk, as affected by temperature and pre-treatments, was studied using dynamic light-scattering. The creaming rate of human milk increased with temperature in the range 5 °C to 40 °C. Freezing human milk at –20 °C and thawing at room temperature had little influence on creaming. Compared with bovine milk, human milk showed a faster creaming rate at 40 °C, but a slower rate at 5 °C, suggesting a lack of cold agglutination; the mechanisms of creaming were also shown to differ in response to heat treatment. This study expands the current knowledge on milk creaming, and may have potential application to storage and handling of human milk in hospitals or homes, therefore supporting optimal nutrition of infants

Individuals with obesity who survive SARS‐CoV‐2 infection have preserved antigen‐specific T cell frequencies

Objective: Obesity is a major risk factor for severe disease in COVID-19, with increased hospitalization, intensive care unit admission, and mortality. This increased impact of COVID-19 in people with obesity (PWO) is likely driven, in part, by the well-described obesity-induced immune dysregulation. Obesity has also been associated with impaired immune memory in many settings, including weakened responses to hepatitis B, tetanus, rabies, and influenza vaccination. Recently, it was reported that PWO who have COVID-19 have reduced IgG antibody titers with defective neutralizing capabilities. However, it remains unknown whether PWO generate durable T cell immunity to SARS-CoV-2. Methods: This study investigated SARS-CoV-2-specific T cell responses in a cohort of 40 patients (n = 20 PWO and n = 20 matched control individuals) who had recovered from COVID-19. T cell (CD4+, CD8+) cytokine responses (IFNγ, TNFα) to SARS-CoV-2 peptide pools (spike, membrane) were determined using multicolor flow cytometry. Results: Circulating T cells specific for SARS-CoV-2 were readily detected in the total cohort. PWO displayed comparable levels of SARS-CoV-2 spike- and membrane-specific T cells, with both T cell subsets responding. Conclusions: These data indicate that PWO who survive COVID-19 generate robust and durable SARS-CoV-2-specific T cell immunity that is equivalent to that seen in those without obesity