Decline in pediatric admission on an isolated island in the COVID-19 pandemic.

BACKGROUND: A decrease in pediatric hospitalizations during the COVID-19 pandemic has been reported worldwide; however, few studies have examined areas with a limited number of COVID-19 cases, where influenced by viral interference by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is minimum. METHODS: We conducted an epidemiological study of pediatric hospitalizations on Sado, an isolated island in Niigata, Japan, that was unique environment with few COVID-19 cases and reliable pediatric admissions monitoring. We compared numbers of monthly hospitalizations and associated diagnoses for the periods April 2016 to March 2020 (pre-pandemic period) and April 2020 to March 2021 (pandemic period). RESULTS: Data were analyzed for 1,144 and 128 patients in the pre-pandemic and pandemic periods, respectively. We observed only three adults and no pediatric COVID-19 cases during the pandemic period. The number of monthly admissions was significantly lower in the pandemic period (median [interquartile ranges (IQR)]: 11.0 [7.0-14.0]) than in the pre-pandemic period (23.0 [20.8-28.3]; P < 0.001). Similar decreases were observed for hospitalizations due to respiratory tract infection (P < 0.01), but not for asthma exacerbation (P = 0.15), and gastrointestinal tract infection (P = 0.33). CONCLUSIONS: Pediatric hospitalizations during the pandemic significantly decreased on an isolated Japanese island where COVID-19 was not endemic and all pediatric admissions were ascertainable. This observation highlights the impact of decreased travel and increased awareness of infection control measures on pediatric hospitalizations due to infectious diseases, not by the SARS-CoV-2 viral interference.

Molecular Dynamics Simulation of Ice Crystal Growth Inhibition by Hexadecyl-trimethyl-ammonium Bromide.

Recent experiments have found hexadecyl-trimethyl-ammonium bromide (CTAB) to have superior ice nucleation inhibition properties [ J. Phys. Chem. B 121, 6580]. The mechanism of how the inhibition takes place remains unclear. Therefore, molecular dynamics was used to simulate ice crystallization of a water/CTAB/ice system. The ice crystallization rate for a pure water system was compared for the basal [0001], first prism [101̅0], and secondary prism plane [112̅0], where the basal plane grew the slowest followed by the first prism plane. When CTAB was added to the ice-liquid water system, crystallization was clearly impeded. Even when ice starts growing away from the CTAB molecule, the hydrophilic head would at some point protrude and get caught in the water/ice interface. Once the head of the CTAB was encapsulated in the advancing interface, the hydrophobic body would wriggle around and disrupt the formation of hydrogen bond networks that are essential for ice growth. When the interface clears the length of the body of the CTAB molecule, ice crystallization resumes at its normal pace. In summary, the inhibition of ice growth is a combination of the hydrophilic head acting as an anchor and the dynamic motion of the hydrophobic tail hindering stable hydrogen bonding for ice growth.

Anti-Ice Nucleating Activity of Surfactants against Silver Iodide in Water-in-Oil Emulsions.

Various water-soluble substances are known as anti-ice nucleating agents (anti-INAs), which inhibit heterogeneous ice nucleation initiated by ice nucleating agents (INAs). Among them, several surfactants are reportedly effective as anti-INAs especially against silver iodide (AgI), which is a typical inorganic INA that induces heterogeneous ice nucleation at relatively high temperatures. In this study, the anti-ice nucleating activities of seven surfactants were examined in emulsified surfactant solutions containing AgI particles. Among previously reported anti-INAs (e.g., antifreeze proteins (AFPs), polyphenol compounds and synthetic polymers), a cationic surfactant used in this study, hexadecyltrimethylammonium bromide (C16TAB), showed the highest anti-ice nucleating activity against AgI. Based on the unique concentration-dependent dispersibility of AgI particles in C16TAB solution, the anti-ice nucleating activity of C16TAB must be caused by the adsorption of C16TAB molecules on AgI surfaces either as a monolayer or a bilayer depending on the C16TAB concentration.