Group Testing Performance Evaluation for SARS-COV-2 Massive Scale Screening and Testing

ABSTRACTThe capacity of current molecular testing convention does not allow high-throughput and community level scans of COVID-19 infections. The diameter in current paradigm of shallow tracing is unlikely to reach the silent clusters that might be as important as the symptomatic cases in the spread of the disease. Group testing is a feasible and promising approach when the resources are scarce and when a relatively low prevalence regime is observed on the population. We employed group testing with a sparse random pooling scheme and conventional group test decoding algorithms both for exact and inexact recovery. Our simulations showed that significant reduction in per case test numbers (or expansion in total test numbers preserving the number of actual tests conducted) for very sparse prevalence regimes is available. Currently proposed COVID-19 group testing schemes offer a gain up to 10X scale-up. There is a good probability that the required scale up to achieve massive scale testing might be greater in certain scenarios. We investigated if further improvement is available, especially in sparse prevalence occurrence where outbreaks are needed to be avoided by population scans. Our simulations show that sparse random pooling can provide improved efficiency gains compared to row-column group testing or Reed-Solomon error correcting codes. Therefore, we propose that special designs for different scenarios could be available and it is possible to scale up testing capabilities significantly.

Estimating long-term settlement of floating stone column groups

Design charts for estimating long-term drained settlement of floating stone column group foundations are presented based on three-dimensional, elastoplastic, finite element analyses. In the analyses, the soft soil behavior is represented by the modified Cam-clay model while the stone column and mat are represented by the Mohr–Coulomb model. The finite element predictions are calibrated against model test results. A detailed parametric study of prototype stone column group foundations of various configurations is carried out to evaluate the relative importance of various foundation parameters on the group response. Next, finite element analyses of corresponding unit cells and single columns are performed. Reasonable correlations of load responses are found between single column and group behavior. Group and single column responses are then used to investigate Sg/S1 relationship with different foundation parameters, where Sg and S1 represent the settlement of the group and single column, respectively.

THE COLUMN GROUP AND ITS LINK INVARIANTS

The column group is a subgroup of the symmetric group on the elements of a finite birack generated by the column permutations in the birack matrix. We use subgroups of the column group associated to birack homomorphisms to define an enhancement of the integral birack counting invariant and give examples which show that the enhanced invariant is stronger than the unenhanced invariant.

Plantar and Calcaneocuboid Joint Pressure after Isolated Medial Column Fusion versus Medial and Lateral Column Fusion: A Biomechanical Study

Background: We compared forefoot and calcaneocuboid pressure in isolated medial column fusion (1-3 tarsometatarsal fusion) versus medial and lateral column fusion (1-5 tarsometatarsal fusion) in a neutral, inversion, and eversion loading model in stance gait phase. Methods: Twelve fresh-frozen cadaveric specimens were cyclically loaded to 720 N at 0.5 Hz for 30 cycles. Plantar and calcaneocuboid joint pressures were measured in neutral, inversion, and eversion in the intact foot, with isolated medial column fusion, and with medial and lateral column fusion. Results: Lateral pressure was higher in the medial and lateral column fusion group than isolated medial column fusion and intact in neutral (55.8 ± 14.8 versus 46.2 ± 13.6 and 45.5 ± 14.8 kPa, respectively) and eversion (80.7 ± 18.4 versus 61.8 ± 13.7 and 60.2 ± 18.2 kPa, respectively) ( p ≤ 0.001). Calcaneocuboid pressure was higher in medial and lateral column fusion than isolated medial column fusion and intact in neutral (1436.7 ± 210.6 versus 1073.7 ± 282.5 and 1084.9 ± 337.6, respectively; p = 0.001) and inversion (1518.3 ± 270.5 versus 1310.5 ± 298.8 and 1237.1 ± 401.9, respectively; p = 0.02). Using combined position data, calcaneocuboid pressure was significantly higher in the medial and lateral column group than in both other groups. The isolated medial column fusion group did not differ significantly from the intact group in any measurement. Conclusion: Medial and lateral column fusion significantly increased lateral and calcaneocuboid pressures with loading compared with isolated medial column fusion and the intact state. No difference was observed between isolated medial column fusion and the intact state. Clinical Relevance: It may be advisable to avoid fusing the lateral column in tarsometatarsal arthrodesis if possible to avoid pressure increase in the forefoot and hindfoot.

The Role of Shoe Design in Ankle Sprain Rates Among Collegiate Basketball Players

Context: Much of the recent focus in shoe design and engineering has been on improving athletic performance. Currently, this improvement has been in the form of “cushioned column systems,” which are spring-like in design and located under the heel of the shoe in place of a conventional heel counter. Concerns have been raised about whether this design alteration has increased the incidence of ankle sprains. Objective: To examine the incidence of lateral ankle sprains in collegiate basketball players with regard to shoe design. Design: Prospective cohort study. Setting: Certified athletic trainers at 1014 National Collegiate Athletic Association (NCAA)-affiliated schools sponsoring basketball during the 2005–2006 regular season were notified of an online questionnaire. Athletic trainers at 22 of the 1014 schools participated. Patients or Other Participants: A total of 230 basketball players (141 males, 89 females; age = 20.2 ± 1.5 years) from NCAA Division I–III basketball programs sustained lateral ankle sprains. Main Outcome Measure(s): Ankle sprain information and type of shoe worn (cushioned column or noncushioned column) were collected via online survey. The incidence of lateral ankle sprains and type of shoes worn were compared using a chi-square analysis. Results: No difference was noted in ankle sprain incidence between groups (χ2 = 2.44, P = .20, relative risk = 1.47, 95% confidence interval [CI] = 0.32, 6.86). The incidence of ankle sprains was 1.33 per 1000 exposures in the cushioned column group (95% CI = 0.62, 3.51) and 1.96 per 1000 exposures in the noncushioned column group (95% CI = 0.51, 4.22). Conclusions: No increased incidence of ankle sprains was associated with shoe design.