Toward Community Surveillance: Detecting Intact SARS-CoV-2 Using Exogeneous Oligonucleotide Labels

The persistence of the COVID-19 pandemic demands a dramatic increase in testing efficiency. Testing pooled samples for SARS-CoV-2 could meet this need; however, the sensitivity of RT-qPCR, the gold standard, significantly decreases with an increasing number of samples pooled. Here, we introduce DIVER, a method that quantifies intact virus and is robust to sample dilution. DIVER first tags viral particles with exogeneous oligonucleotides, then captures the tagged particles on ACE2-functionalized beads, and finally quantifies the oligonucleotide tags using qPCR. Using spike-presenting liposomes and Spike-pseudotyped lentivirus as SARS-CoV-2 models, we show that DIVER can detect 1×105 liposomes and 100 pfu lentivirus and can successfully identify positive samples in pooling experiments. Overall, DIVER is well-positioned for efficient sample pooling and expanded community surveillance.

A Study of Transmission Error Modeling and Preload Compensation for the Cable-Driven Sheaves Used in Space Docking Locks

ABSTRACTThe transmission error of cable-driven sheaves (CDS) used in space docking locks directly affects the synchronous docking of two spacecraft, which is guaranteed mainly by the preload applied to their serial cables. But it is difficult controlled precisely because of the complicated cable deformation and operating conditions. The synchronous testing efficiency of the docking locks is inevitably influenced, correspondingly. This paper proposes a prediction model for the transmission error of CDS based on their cable deformation. In this model, the deformations of non- and free sectional cables are both modified on finite element analysis, which are respectively derived from classical Capstan equation and Hooke’s law for them without considering the effects of the friction coefficient between wire strands. Based on the proposed model, the relationships between the transmission error and dominating factors are analyzed. Then the preload compensation for transmission error is obtained at the engaging and locking angles of the docking locks, respectively. Experiments validate the model. This can provide a valuable reference in controlling the transmission error of CDS and improving the assembly efficiency of docking locks.

Real-time Screening of Specimen Pools for Coronavirus Disease 2019 (COVID-19) Infection at Sanya Airport, Hainan Island, China

A 10:1 pooled test strategy on-site at an airport of China was pursued, resulting in increased test throughput, limited use of reagents, and increased testing efficiency without loss of sensitivity. This testing approach has the potential to reduce the need for contact tracing when the results are delivered first time.

Optimally Pooled Viral Testing

It has long been known that pooling samples may be used to minimize the total number of tests required in order to identify each infected individual in a population. Pooling is most advantageous in populations with low infection probability, but is expected to remain better than non-pooled testing in populations with an infection probability up to 30%. Additional testing efficiency may be realized by performing a second round of pooled testing, thus reducing the average number of tests required to uniquely identify each infected individual in a population with 1% infection from 20 to 14 out of 100, and from 6 to 4 when the infection probability is 0.1%. These best case predictions, obtained assuming perfect test accuracy and specificity, provide a quantitative measure of the optimal pool size and expected testing efficiency gains in populations with infection probabilities ranging from 0.1% to 30%, and are supported by recent COVID-19 empirical detection sensitivity and optimized pool size studies. Although large pools are most advantageous for testing populations with very low infection probabilities, they are predicted to become highly non-optimal with increasing infection probability, while pool sizes smaller than 10 remain near-optimal over a broader range of infection probabilities.

Thread Scheduling Sequence Generation Based on All Synchronization Pair Coverage Criteria

Testing multi-thread programs becomes extremely difficult because thread interleavings are uncertain, which may cause a program getting different results in each execution. Thus, Thread Scheduling Sequence (TSS) is a crucial factor in multi-thread program testing. A good TSS can obtain better testing efficiency and save the testing cost especially with the increase of thread numbers. Focusing on the above problem, in this paper, we discuss a kind of approach that can efficiently generate TSS based on the concurrent coverage criteria. First, we give a definition of Synchronization Pair (SP) as well as all Synchronization Pairs Coverage (ASPC) criterion. Then, we introduce the Synchronization Pair Thread Graph (SPTG) to describe the relationships between SPs and threads. Moreover, this paper presents a TSS generation method based on the ASPC according to SPTG. Finally, TSSs automatic generation experiments are conducted on six multi-thread programs in Java Library with the help of Java Path Finder (JPF) tool. The experimental results illustrate that our method not only generates TSSs to cover all SPs but also requires less state number, transition number as well as TSS number when satisfying ASPC, compared with other three widely used TSS generation methods. As a result, it is clear that the efficiency of TSS generation is obviously improved.