Studies of novel coronavirus disease (COVID-19) have reported varying estimates of epidemiological parameters including serial interval distributions, i.e., the time between illness onset in successive cases in a transmission chain, and reproduction numbers. By compiling a line-list database of transmission pairs in mainland China, we show that mean serial intervals of COVID-19 have shortened substantially from 7.8 days to 2.6 days within a month (January 9 to February 13, 2020). This change is driven by enhanced non-pharmaceutical interventions, in particular case isolation. We also show that using real-time estimation of serial intervals allowing for variation over time, provides more accurate estimates of reproduction numbers than using conventionally fixed serial interval distributions. These findings could improve assessment of transmission dynamics, forecasting future incidence, and estimating the impact of control measures.

Cell membrane dielectric properties of five different cultivated cell lines and human peripheral blood mononuclear cells (PBMC) were determined from dielectrophoretic crossover frequency measurements on a 5 x 5 microelectronic chip array. Based on distinct dielectric property differences between individual cell types, efficient cell separations were achieved by dielectrophoresis on this 5 x 5 array, which included separation of monocytic cells (U937) or human T cell leukemia virus type 1 (HTLV-1) tax-transformed cells (Ind-2) from PBMC, as well as separation of neuroblastoma cells (SH-SY5Y) from glioma cells (HTB). The purity of dielectrophoretically separated cells can be greater than 95%. Expression profiles of IL-1, TNF-alpha, and TGF-beta genes for U937 cells mixed with PBMC before and after the separation were determined by a means of electric field-facilitated hybridization on a 10 x 10 microelectronic chip array. By using the expression levels of pure U937 cells as a control, it was shown that the gene expression profiles of the postseparation cells were significantly different from those of the preseparation cell mixtures. The increase in gene expression levels for U937 cells upon lipopolysaccharide induction could be accurately determined only in the postseparation cells, while the preseparation samples masked these changes. Furthermore, by cultivating the separated HTB and SH-SY5Y cells and measuring expression of the stress-related gene c-fos, dielectrophoretic forces were shown to have little effect on cell survival and stress. The presented approach of using microelectronic chip arrays for both cell separation and gene expression profiling provides a great potential for accurate genetic analysis of specific cell subpopulations in heterogeneous samples.

Background Knowledge on the epidemiological features and transmission patterns of COVID-19 is accumulating. Detailed line-list data with household settings can advance the understanding of COVID-19 transmission dynamics. Methods A unique database with detailed demographic characteristics, travel history, social relationships, and epidemiological timelines for 1,407 transmission pairs that formed 643 transmission clusters in mainland China was reconstructed from 9,120 COVID-19 confirmed cases reported during January 15 - February 29, 2020. Statistical model fittings were used to identify the super-spreaders and estimate serial interval distributions. Age and gender-stratified hazard of infection were estimated for household versus non-household transmissions. Results There were 34 primary cases identified as super-spreaders, with 5 super-spreading events occurred within households. Mean and standard deviation of serial intervals were estimated as 5.0 (95% CrI: 4.4, 5.5) and 5.2 (95% CrI: 4.9, 5.7) days for household transmissions and 5.2 (95% CrI: 4.6, 5.8) and 5.3 (95% CrI: 4.9, 5.7) days for non-household transmissions, respectively. Hazard of being infected outside of households is higher for age between 18 and 64 years, whereas hazard of being infected within households is higher for young and old people. Conclusions Non-negligible frequency of super-spreading events, short serial intervals, and a higher risk of being infected outside of households for male people of working age indicate a significant barrier to the identification and management of COVID-19 cases, which requires enhanced non-pharmaceutical interventions to mitigate this pandemic.

We have developed a method for anchored amplification on a microchip array that allows amplification and detection of multiple targets in an open format. Electronic anchoring of sets of amplification primers in distinct areas on the microchip permitted primer-primer interactions to be reduced and distinct zones of amplification created, thereby increasing the efficiency of the multiplex amplification reactions. We found strand displacement amplification (SDA) to be ideal for use in our microelectronic chip system because of the isothermal nature of the assay, which provides a rapid amplification system readily compatible with simple instrumentation. Anchored SDA supported multiplex DNA or RNA amplification without decreases in amplification efficiency. This microelectronic chip-based amplification system allows multiplexed amplification and detection to be performed on the same platform, streamlining development of any nucleic acid-based assay.

Background The widespread pandemic of novel coronavirus disease 2019 (COVID-19) poses an unprecedented global health crisis. In the United States (US), different state governments have adopted various combinations of non-pharmaceutical public health interventions (NPIs), such as non-essential business closures and gathering bans, to mitigate the epidemic from February to April, 2020. Quantitative assessment on the effectiveness of NPIs is greatly needed to assist in guiding individualized decision making for adjustment of interventions in the US and around the world. However, the impacts of these approaches remain uncertain. Methods Based on the reported cases, the effective reproduction number (Rt) of COVID-19 epidemic for 50 states in the US was estimated. Measurements on the effectiveness of nine different NPIs were conducted by assessing risk ratios (RRs) between Rt and NPIs through a generalized linear model (GLM). Results Different NPIs were found to have led to different levels of reduction in Rt. Stay-at-home contributed approximately 51% (95% CI 46–57%), wearing (face) masks 29% (15–42%), gathering ban (more than 10 people) 19% (14–24%), non-essential business closure 16% (10–21%), declaration of emergency 13% (8–17%), interstate travel restriction 11% (5–16%), school closure 10% (7–14%), initial business closure 10% (6–14%), and gathering ban (more than 50 people) 7% (2–11%). Conclusions This retrospective assessment of NPIs on Rt has shown that NPIs played critical roles on epidemic control in the US in the past several months. The quantitative results could guide individualized decision making for future adjustment of NPIs in the US and other countries for COVID-19 and other similar infectious diseases.

Link prediction is the problem of predicting the existence and location of unknown links from uncertain structural information of a network. Most existing accuracy measures do not consider the role of time evolution within the network. Moreover, almost all existing methods use indirect links to infer and evaluate the validity of links. We introduce time as a parameter for link prediction accuracy measures, and we modify the structure of the link prediction algorithms to exploit information of the known direct links for link prediction. We find that the direct link algorithm performs better than the indirect link algorithm for a range of time varying networks. We show that the network structure plays a more important role than weights for links prediction. In addition, our analysis finds that the number of common neighbours also plays an important role for the so-called weak-ties phenomenon.

A novel photonic generation of power-efficient ultrawideband (UWB) pulse by incoherent summation of two asymmetric monocycle pulses with inverted polarities is experimentally demonstrated. The principles of multiple cross-phase modulations in a highly nonlinear fiber and multiple phase modulation to intensity modulation conversions in a commercially available arrayedwaveguide grating are used. The combined UWB pulse exploiting spectral efficiency of 50.59% in experiment is fully compliant with the Federal Communications Commission (FCC) spectral mask without power attenuation. The FCC-compliant UWB pulse gains larger than 11.5-and 6-dB improvement against monocycle and doublet pulses after power attenuation to respect the FCC spectral mask, respectively. Such a power-efficient UWB pulse with pulse duration of approximately 320 ps has potential to achieve high-speed transmission without pulse overlapping and obvious distortion. Index Terms-Microwave photonics, nonlinear signal processing, ultra-wideband (UWB)-over-fiber, wireless technology.

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