[The role of large-scale testing platform in the prevention and control of the COVID-19 pandemic: an empirical study based on a novel numerical model].

Objective: China adopted an unprecedented province-scale quarantine since January 23rd 2020, after the novel coronavirus (COVID-19) broke out in Wuhan in December 2019. Responding to the challenge of limited testing capacity, large-scale (>20 000 tests per day) standardized and fully-automated laboratory (Huo-Yan) was built as an ad-hoc measure. There is so far no empirical data or mathematical model to reveal the impact of the testing capacity improvement since quarantine. Methods: Based on the suspected case data released by the Health Commission of Hubei Province and the daily testing data of Huo-Yan Laboratory, the impact of detection capabilities on the realization of "clearing" and "clearing the day" of supected cases was simulated by establishing a novel non-linear and competitive compartments differential model. Results: Without the establishment of Huo-Yan, the suspected cases would increase by 47% to 33 700, the corresponding cost of quarantine would be doubled, the turning point of the increment of suspected cases and the achievement of "daily settlement" (all newly discovered suspected cases are diagnosed according to the nucleic acid testing result) would be delayed for a whole week and 11 days. If the Huo-Yan Laboratory could ran at its full capacity, the number of suspected cases could start to decrease at least a week earlier, the peak of suspected cases would be reduced by at least 44%, and the quarantine cost could be reduced by more than 72%. Ideally, if a daily testing capacity of 10 500 tests was achieved immediately after the Hubei lockdown, "daily settlement" for all suspected cases could be achieved. Conclusions: Large-scale, standardized clinical testing platform, with nucleic acid testing, high-throughput sequencing, and immunoprotein assessment capabilities, need to be implemented simultaneously in order to maximize the effect of quarantine and minimize the duration and cost of the quarantine. Such infrastructure, for both common times and emergencies, is of great significance for the early prevention and control of infectious diseases.

Biological background of the genomic variations of cf-DNA in healthy individuals.

BACKGROUND: Cell-free DNA (cf-DNA)-based liquid biopsy is emerging as a revolutionary new method in individualized cancer treatment and prognosis monitoring, although detecting early-stage cancers using cf-DNA remains challenging, partially because of the undefined biological background of cf-DNA. MATERIALS AND METHODS: We investigated somatic mutations in the cf-DNA of 259 cancer-free individuals with a median age of 47 years using an endogenous barcoding duplex method with an ultralow base error rate (2 × 10-7) and compared the variant allele frequencies (VAFs) of these mutations between the cf-DNA and the corresponding blood cell DNA. RESULTS: Sixty percent (155/259) of the samples showed at least one nonsynonymous mutation on either of two similar target panels covering 508 and 559 cancer-related genes. For individuals older than 50 years of age, the positive rate increased to 76%. Most cf-DNA mutations were also present at similar VAFs in the paired blood cell DNA. The most frequently mutated genes were driver genes of hematologic malignancies, including DNMT3A, TET2, AXSL1, and JAK2. However, the other 58.4% (192/329) of the mutations were likely 'passenger mutations' of clonal hematopoiesis, including mutations in NOTCH2, FAT3, EXT2, ERBB4, and ARID2, which are driver genes of solid tumors. CONCLUSION: Hematopoietic clone-derived mutations, including 'driver mutations' and 'passenger mutations', are prevalent in the cf-DNA of both healthy individuals and cancer patients and may be a potential source of false positives in the liquid biopsy. Our results also suggest the ineffectiveness for distinguishing clonal hematopoietic mutations of low VAF (≤0.1%) from tumor-derived mutations using conventional next-generation sequencing of blood cell DNA. However, an error correction model with an ultralow error rate and high coverage depth is required for blood cell DNA sequencing, which is difficult and costly to achieve with current technologies.

Sorption behaviour of neptunium in marine and fresh water bottom sediments in Far East area of Russia (Lake Khanka and Amur Bay).

The concentration and sorption behavior of 237Np on the bottom sediments of water bodies in the Far East region of Russia (Lake Khanka and Peter the Great Bay) were studied for the first time. The 237Np concentrations vary from 1.06 × 10-6 to 4.43 × 10-5 mBq g-1 in the bottom sediments of Lake Khanka and from 1.05 × 10-4 to 2.52 × 10-3 mBq g-1 for Amur Bay. The experiment on the adsorption of Np on marine and lake sediment showed that it is sorbed through complexation with silicates (albite, leucite). The Np sorption isotherm on marine sediments is described by the Langmuir equation; the distribution coefficients (Kd) of Np vary from 57 to 588 mL g-1. For lake sediments, the isotherm is described by the Henry equation; the Kd value reaches 935 mL g-1.

[Determination of gibberellin A3 by reversed phase high performance liquid chromatography].

The analysis of gibberellin GA3 by high performance liquid chromatography (HPLC) was carried out with mu Bondapak C18 column. The developed reversed phase HPLC procedure enables the separation of different GAs with high resolution by means of ionic suppression, including the separation of double bond isomers GA1 and GA3. This method is convenient (without the necessity of derivatization), rapid (15 min for one overall run), sensitive (0.5 microgram is sufficient for precise assay), and has fine linearity (r = 0.999, n = 5) and reproducibility (relative standard deviation < 2%, n = 4).