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Problem definition: We study a robust screening problem where a seller attempts to sell a product to a buyer knowing only the moment and support information of the buyer's valuation distribution. The objective is to maximize the competitive ratio relative to an optimal hindsight policy equipped with full valuation information. Methodology/results: We formulate the robust screening problem as a linear programming problem, which can be solved efficiently if the support of the buyer's valuation is finite. When the support of the buyer's valuation is continuous and the seller knows the mean and the upper and lower bounds of the support for the buyer's valuation, we show that the optimal payment is a piecewise polynomial function of the valuation with a degree of at most two. Moreover, we derive the closed-form competitive ratio corresponding to the optimal mechanism. The optimal mechanism can be implemented by a randomized pricing mechanism whose price density function is a piecewise inverse function adjusted by a constant. When the mean and variance are known to the seller, we propose a feasible piecewise polynomial approximation of the optimal payment function with a degree of at most three. We also demonstrate that the optimal competitive ratio exhibits a logarithmic decay with respect to the coefficient of variation of the buyer's valuation distribution. Managerial implications: Our general framework provides an approach to investigating the value of moment information in the robust screening problem. We establish that even a loose upper bound of support or a large variance can guarantee a good competitive ratio. Funding: The research of S. Wang is partially supported by the National Natural Science Foundation of China [Grant 72394395]. The research of S. Liu is partly supported by the National Natural Science Foundation of China [Grant NSFC-72072117]. Supplemental Material: The online appendix is available at https://doi.org/10.1287/msom.2023.0072. [ABSTRACT FROM AUTHOR]

Background: The mechanisms and risk factors underlying ovarian cancer (OC) remain under investigation, making the identification of new prognostic biomarkers and improved predictive factors critically important. Recently, circulating metabolites have shown potential in predicting survival outcomes and may be associated with the pathogenesis of OC. However, research into their genetic determinants is limited, and there are some inadequacies in understanding the distinct subtypes of OC. In this context, we conducted a Mendelian randomization study aiming to provide evidence for the relationship between genetically determined metabolites (GDMs) and the risk of OC and its subtypes. Methods: In this study, we consolidated genetic statistical data of GDMs with OC and its subtypes through a genome-wide association study (GWAS) and conducted a two-sample Mendelian randomization (MR) analysis. The inverse variance weighted (IVW) method served as the primary approach, with MR-Egger and weighted median methods employed for cross-validation to determine whether a causal relationship exists between the metabolites and OC risk. Moreover, a range of sensitivity analyses were conducted to validate the robustness of the results. MR-Egger intercept, and Cochran's Q statistical analysis were used to evaluate possible heterogeneity and pleiotropy. False discovery rate (FDR) correction was applied to validate the findings. We also conducted a reverse MR analysis to validate whether the observed blood metabolite levels were influenced by OC risk. Additionally, metabolic pathway analysis was carried out using the MetaboAnalyst 5.0 software. Results: In MR analysis, we discovered 18 suggestive causal associations involving 14 known metabolites, 8 metabolites as potential risk factors, and 6 as potential cancer risk reducers. In addition, three significant pathways, "caffeine metabolism," "arginine biosynthesis," and "citrate cycle (TCA cycle)" were associated with the development of mucinous ovarian cancer (MOC). The pathways "caffeine metabolism" and "alpha-linolenic acid metabolism" were associated with the onset of endometrioid ovarian cancer (OCED). Conclusions: Our MR analysis revealed both protective and risk-associated metabolites, providing insights into the potential causal relationships between GDMs and the metabolic pathways related to OC and its subtypes. The metabolites that drive OC could be potential candidates for biomarkers. [ABSTRACT FROM AUTHOR]

Background: Circulating cytokines have been associated with colorectal cancer (CRC). However, their causal correlation remains undetermined. This investigation uses genetic data to evaluate the mechanism that links circulating cytokines and CRC via Mendelian Randomization (MR). Methods: A two-sample MR evaluation was carried out to investigate the mechanism associating circulating cytokines and CRC in individuals of European ancestry. The Genome-wide association studies statistics, which are publically accessible, were used. Eligible instrumental SNPs that were significantly related to the circulating cytokines were selected. Multiple MR analysis approaches were carried out, including Simple Mode, inverse variance weighted (IVW), MR-Egger, Weighted Mode, Weighted Median, and MR pleiotropy residual sum and outlier (MR-PRESSO) methods. Results: The evidence supporting the association of genetically predicted circulating levels with the increased risk of CRC was revealed; these included vascular endothelial growth factor (OR = 1.352, 95% CI: 1.019–1.315, P = 0.024), interleukin-12p70 (OR = 1.273, 95% CI: 1.133–1.430, P = 4.68×10−5), interleukin-13 (OR = 1.149, 95% CI: 1.012–1.299, P = 0.028), interleukin-10 (OR = 1.230, 95% CI: 1.013–1.493, P = 0.037), and interleukin-7 (OR = 1.191, 95% CI: 1.023–1.386 P = 0.024). Additionally, MR analysis negative causal association between macrophage colony stimulating factor and CRC (OR = 0.854, 95% CI: 0.764–0.955, P = 0.005). The data from Simple Mode, Weighted Median, MR-Egger, and Weighted Mode analyses were consistent with the IVW estimates. Furthermore, the sensitivity analysis indicated that the presence of no horizontal pleiotropy to bias the causal estimates. Conclusion: This investigation identified a causal association between circulating cytokines levels risk of CRC and may provide a deeper understanding of the pathogenesis of CRC, as well as offer promising leads for the development of novel therapeutic targets for CRC. [ABSTRACT FROM AUTHOR]

Background: Esketamine has higher potency, stronger receptor affinity, a stronger analgesic effect, a higher in vivo clearance rate, and a lower incidence of adverse reactions when compared to ketamine. However, there have been few ketamine studies to assess patient-centered, overall recovery outcomes from the perspective of patients with colorectal cancer. Methods: This was a prospective, randomized controlled trial. Ninety-two patients undergoing laparoscopic radical resection of colorectal cancer were randomly assigned to either the esketamine (K group) or non-eskatamine (C group) group. After anesthesia induction, a loading dose of 0.25 mg/kg was administered, followed by continuous infusion at a rate of 0.12 mg.kg-1.h-1 until closure of surgical incisions in the K group. In the C group, an equivalent volume of normal saline was infused. The primary outcome was quality of recovery at 24 h after surgery, as measured by the Quality of Recovery-15 (QoR-15) scale. The QoR-15 was evaluated at three timepoints: before (Tbefore), 24 h (T24h) and 72 h (T72h) after surgery. Main results: A total of 88 patients completed this study. The total QoR-15 scores in K group (n = 45) were higher than in the C group (n = 43) at 24 h: 112.33 ± 8.79 vs. 103.93 ± 9.03 (P = 0.000) and at 72 h: 118.73 ± 7.82 vs. 114.79 ± 7.98 (P = 0.022). However, the differences between the two groups only had clinical significance at 24 h after surgery. Among the five dimensions of the QoR-15, physical comfort (P = 0.003), emotional state (P = 0.000), and physical independence (P = 0.000) were significantly higher at 24 h in the K group, and physical comfort (P = 0.048) was higher at 72 h in the K group. Conclusions: This study found that intraoperative intravenous low-dose esketamine could improve the early postoperative quality of recovery in patients undergoing laparoscopic radical resection of colorectal cancer from the perspective of patients. [ABSTRACT FROM AUTHOR]

In manufacturing and services, random problems arise that disrupt normal operations. Organizations must resolve these problems in a timely and cost-efficient manner—which can be a daunting task. A typical management response is assigning escalation routes whereby the lowest tier initially owns a problem that may later be escalated to higher tiers. To minimize the costs associated with these problems, we consider a management policy that specifies a time limit beyond which problems must move up a tier; the setting is formulated as a stochastic dynamic program. For scenarios involving a single problem type, we find that optimal time limits can exist when the problem service times are generally distributed or correlated and when the marginal delay cost increases with time; we also characterize the single–problem type, multi-tier optimal solution when the marginal delay cost is constant. When multiple types of problems are pooled together, we show that a time-limit–based approach is robust to various probability distributions of service times and performs reasonably well even when the problem type is unidentified ex ante. Finally, we derive comparative statics on how parameter values, problem characteristics, and the composition of problems each affect the optimal time limit. [ABSTRACT FROM AUTHOR]

Problem definition: We consider a revenue management problem that arises from the selling of high-speed train tickets in China. Compared with traditional network revenue management problems, the new feature of our problem is the assign-to-seat restriction. That is, each request, if accepted, must be assigned instantly to a single seat throughout the whole journey, and later adjustment is not allowed. When making decisions, the seller needs to track not only the total seat capacity available, but also the status of each seat. Methodology/results: We build a modified network revenue management model for this problem. First, we study a static problem in which all requests are given. Although the problem is NP-hard in general, we identify conditions for solvability in polynomial time and propose efficient approximation algorithms for general cases. We then introduce a bid-price control policy based on a novel maximal sequence principle. This policy accommodates nonlinearity in bid prices and, as a result, yields a more accurate approximation of the value function than a traditional bid-price control policy does. Finally, we combine a dynamic view of the maximal sequence with the static solution of a primal problem to propose a "re-solving a dynamic primal" policy that can achieve uniformly bounded revenue loss under mild assumptions. Numerical experiments using both synthetic and real data document the advantage of our proposed policies on resource-allocation efficiency. Managerial implications: The results of this study reveal connections between our problem and traditional network revenue management problems. Particularly, we demonstrate that by adaptively using our proposed methods, the impact of the assign-to-seat restriction becomes limited both in theory and practice. Funding: S. Liu's research is partly supported by the National Natural Science Foundation of China (NSFC) [Grant NSFC-72072117]. Z. Wang's research is partly supported by the NSFC [Grant NSFC-72150002]. Supplemental Material: The online appendix is available at https://doi.org/10.1287/msom.2023.1188. [ABSTRACT FROM AUTHOR]

Nonvolatile resistive switching memristance devices with a high on/off ratio are desirable for nanoelectronics such as resistive random‐access memory (RRAM) and in‐memory computing. Here, bipolar resistive switching in point‐contacted W/LaAlO3/SrTiO3(111) heterojunctions is reported, in which a Schottky barrier is formed at the metal/oxides interface, and 2d electron gas is formed at the interface of perovskite oxides. A negative differential resistance is observed in the RESET process. The result shows that the observed resistive switching is strongly associated with oxygen‐vacancies (OVs) in oxides with dominating contributions from electron hopping between OV trap sites, and can be controlled by oxygen annealing and electron injection. Remarkably, a method is developed by continuous RESET processes to increase the high resistance state by 1–3 orders of magnitude, with an on/off ratio enhanced from ≈10 to ≈104. The work provides a promising pathway to understand conduction mechanism of oxides memristors and promote its application in RRAM and in‐memory computing. [ABSTRACT FROM AUTHOR]

This paper studies a decentralized assembly system with two types of independent component suppliers: one type, so-called commanding suppliers, has strong market power and sets the component price in a push contract offered to the assembler; the other type, subordinate suppliers, has weak market power and accepts a pull contract with the component price set by the assembler. We analyze how direct supply base reduction of component suppliers through supplier clustering can affect the profitability of the assembler and the component suppliers, and we show that direct supply base reduction through clustering of commanding suppliers is generally beneficial to the assembler. Direct supply base reduction through clustering of subordinate suppliers also benefits the assembler, except when the clustering would add another commanding supplier to the system. In that case, our numerical results show that such clustering would likely improve the assembler's profitability when a product's profit margin is low and when clustering yields a reduction in the assembler's coordination costs. We also give sufficient conditions under which direct supply base reduction through supplier clustering benefits also the suppliers involved in the clustering. [ABSTRACT FROM AUTHOR]

With the rapid development of computing technology, using parallel computing to solve large-scale ranking-and-selection (R&S) problems has emerged as an important research topic. However, direct implementation of traditionally fully sequential procedures in parallel computing environments may encounter various problems. First, the scheme of all-pairwise comparisons, which is commonly used in fully sequential procedures, requires a large amount of computation and significantly slows down the selection process. Second, traditional fully sequential procedures require frequent communication and coordination among processors, which are also not efficient in parallel computing environments. In this paper, we propose three modifications on one classical fully sequential procedure, Paulson's procedure, to speed up its selection process in parallel computing environments. First, we show that if no common random numbers are used, then we can significantly reduce the computation spent on all-pairwise comparisons at each round. Second, by batching different alternatives, we show that we can reduce the communication cost among the processors, leading the procedure to achieve better performance. Third, to boost the procedure's final-stage selection, when the number of surviving alternatives is less than the number of processors, we suggest to sample all surviving alternatives to the maximal number of observations that they should take. We show that, after these modifications, the procedure remains statistically valid and is more efficient compared with existing parallel procedures in the literature. Summary of Contribution: Ranking and selection (R&S) is a branch of simulation optimization, which is an important area of operations research. In recent years, using parallel computing to solve large-scale R&S problems has emerged as an important research topic, and this research topic is naturally situated in the intersection of computing and operations research. In this paper, we consider how to improve a fully sequential R&S procedure, namely, Paulson's procedure, to reduce the high computational complexity of all-pairwise comparisons and the burden of frequent communications and coordination, so that the procedure is more suitable and more efficient in solving large-scale R&S problems using parallel computing environments that are becoming ubiquitous and accessible for ordinary users. The procedure designed in this paper appears more efficient than the ones available in the literature and is capable of solving R&S problems with over a million alternatives in a parallel computing environment with 96 processors. The paper also extended the theory of R&S by showing that the all-pairwise comparisons may be decomposed so that the computational complexity may be reduced significantly, which drastically improves the efficiency of all-pairwise comparisons as observed in numerical experiments. [ABSTRACT FROM AUTHOR]

We study the incentive design decision of a firm that outsources its online marketing and operational business lines to professional external and internal service providers under the principalagent framework. Customer satisfaction is represented as the composite of the agents' sales and quality-control efforts via the disconfirmation model, and is introduced into the demand model and incentive contracts. Two scenarios corresponding to whether the brand owner delegates business to a single agent or to multiple agents are studied. We derive the brand owner's optimal contracts and the agents' effort levels and conduct extensive sensitivity analyses regarding the influences of model parameters. We find that increases in the measure accuracy of customer satisfaction can bring significant benefit to the firm's profitability, and explore how it is affected by system factors. Specifically, the benefit is more substantial when the marginal cost of quality-control effort is relatively smaller than the marginal cost of sales effort. An interesting discovery is that the brand owner always earns more profit by outsourcing business to multiple agents than to a single agent, mainly because of his inflexibility in reaching a balance between inducing higher effort levels and providing a sufficient risk premium in the singe-agent case. This profit gap can be expanded by incentivizing both agents on customer satisfaction measures, and is shown quite significant under certain settings in the numerical studies. [ABSTRACT FROM AUTHOR]

Effective therapies are urgently needed for the SARS-CoV-2 pandemic. Chloroquine has been proved to have antiviral effect against coronavirus in vitro. In this study, we aimed to assess the efficacy and safety of chloroquine with different doses in COVID-19. In this multicenter prospective observational study, we enrolled patients older than 18 years old with confirmed SARS-CoV-2 infection excluding critical cases from 12 hospitals in Guangdong and Hubei Provinces. Eligible patients received chloroquine phosphate 500 mg, orally, once (half dose) or twice (full dose) daily. Patients treated with non-chloroquine therapy were included as historical controls. The primary endpoint is the time to undetectable viral RNA. Secondary outcomes include the proportion of patients with undetectable viral RNA by day 10 and 14, hospitalization time, duration of fever, and adverse events. A total of 197 patients completed chloroquine treatment, and 176 patients were included as historical controls. The median time to achieve an undetectable viral RNA was shorter in chloroquine than in non-chloroquine (absolute difference in medians −6.0 days; 95% CI −6.0 to −4.0). The duration of fever is shorter in chloroquine (geometric mean ratio 0.6; 95% CI 0.5 to 0.8). No serious adverse events were observed in the chloroquine group. Patients treated with half dose experienced lower rate of adverse events than with full dose. Although randomized trials are needed for further evaluation, this study provides evidence for safety and efficacy of chloroquine in COVID-19 and suggests that chloroquine can be a cost-effective therapy for combating the COVID-19 pandemic. [ABSTRACT FROM AUTHOR]

Background: The outbreak of COVID-19 (caused by SARS-Cov-2) is very serious, and no effective antiviral treatment has yet been confirmed. The adage "old drug, new trick" in this context may suggest the important therapeutic potential of existing drugs. We found that the lopinavir/ritonavir treatment recommended in the fifth edition of the Treatment Plan of China can only help to improve a minority of throat-swab nucleic-acid results (3/15) in hospitals. Our previous use of chloroquine to treat patients with COVID-19 infection showed an improvement in more throat-swab nucleic-acid results (5/10) than the use of lopinavir/ritonavir.Methods/design: This is a prospective, open-label, randomized controlled, multicenter clinical study. The study consists of three phases: a screening period, a treatment period of no more than 10 days, and a follow-up period for each participant. Participants with COVID-19 infection who are eligible for selection for the study will be randomly allocated to the trial group or the control group. The control group will be given lopinavir/ritonavir treatment for no more than 10 days. The trial group will be given chloroquine phosphate treatment for no more than 10 days. The primary outcome is the clinical recovery time at no more than 28 days after the completion of therapy and follow-up. The secondary outcomes include the rate of treatment success after the completion of therapy and follow-up, the time of treatment success after no more than 28 days, the rate of serious adverse events during the completion of therapy and follow-up, and the time to return to normal temperature (calculated from the onset of illness) during the completion of therapy and follow-up. Comparisons will be performed using two-sided tests with a statistical significance level of 5%.Discussion: This experiment should reveal the efficacy and safety of using chloroquine versus lopinavir/ritonavir for patients with mild/general COVID-19 infection. If the new treatment including chloroquine shows a higher rate of throat-swab SARS-CoV-2 real-time fluorescent reverse transcription polymerase chain reaction (RT-PCR) negativity and is safe, it could be tested as a future COVID-19 treatment.Trial Registration: Chinese Clinical Trial Registry, ID: ChiCTR2000029741 . Registered on 11 February 2020. [ABSTRACT FROM AUTHOR]

In some fully sequential ranking and selection procedures, such as the KN procedure and Rinott's procedure, some initial samples must be taken to estimate the variance. We analyze the impact of the initial sample size (ISS) on the total sample size and propose an algorithm to calculate the ISS in this type of procedure. To better illustrate our approach, we implement this algorithm on the KN procedure and propose the KN-ISS procedure. Comprehensive numerical experiments reveal that this procedure can significantly improve the efficiency compared with the KN procedure and still deliver the desired probability of correct selection. [ABSTRACT FROM AUTHOR]

ABSTRACT The effect of thermal treatment over a wide range of temperature (130-280°C) on the crystallization behavior of nylon 6 was studied by using DSC, FTIR, and polarized light microscope equipped with a hot stage. The crystallization and the subsequent melting behavior of the nylon 6 samples treated at different temperatures ( Ts) were classified into four types. When Ts was higher than 236°C or lower than 213°C, the crystallization behavior of nylon 6 was insensitive to the variation of Ts. When Ts was in the range of 213-235°C, the crystallization behavior was sensitive to the change of Ts. The polarized light microscopic experiments have demonstrated that a large amount of tiny ordered nylon 6 segments/cluster persisted when nylon 6 film are heated to 231°C. Consequently, the fastest crystallization speed was observed. As Ts was between 214 and 223°C, both the Tm and the Δ Hm were higher than those of the nylon 6 samples treated at other temperature. The polarized light microscopic investigations have also demonstrated that molten nylon 6 crystallizes by using the un-molten nylon 6 crystals as nucleation center at 220°C. Crystallization at higher temperature produces nylon 6 with thicker crystalline lamella. The above results are helpful for rational design of thermal treatment procedure to obtain nylon 6 with different crystalline features. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42413. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the formation of the third-phase in tertiary amine (N235)-PtCl-HCl system and the microscopic phase structural evolution of platinum-loaded organic phases before and after the occurrence of the third-phase. The third-phase is characterized by various spectroscopic techniques, and the small angle X-ray scattering (SAXS) experiments demonstrate the appearance of nano-aggregates, i.e., water-in-oil reversed micelles, in the third phase. The experimental results indicate that (1) formation of the third phase is related to the aggregation behaviors of nano-reversed micelles in which a super-concentrated hydrochloric acid formed with the H+ to H2O molar ratio being much higher than that of the conventional 37 wt% saturated hydrochloric acid. (2) The occurrence of the super-concentrated HCl results in a great amount of H+ and Cl− ions enriched and confined within the nano-water pools of W/O reversed micelles in third phase. Therefore, the coordination behaviors of platinum complex ions in that super-concentrated hydrochloric acid are very different from their corresponding behaviors in bulk aqueous solutions. It is possible that H+ ions participate in the formation of such complexes as H m PtCl in the super-concentrated hydrochloric acid. (3) The relative contents of various H m PtCl complexes are different corresponding to the H+ ion concentrations in confined nano-water pools. The association ability of the acidified tertiary amine N235 molecules (R3NH+) with various H m PtCl complexes plays an important role in affecting the platinum extraction behaviors. [ABSTRACT FROM AUTHOR]

Recently we have successfully produced fine denier PA6 fibers by using additives containing lanthanide compounds. Meanwhile, crystallization and phase transition of PA6 fibers during spinning and drawing processes were investigated. During the spinning process, β phase crystal could be obtained in as-spun PA6 fibers which were produced with relatively high melt draw ratio, while γ phase crystal predominated when the melt draw ratio was relatively low. β phase crystal, whose behaviors are similar with those of γ phase by FT-IR and XRD characterization, could be transformed to α form easily when PA6 fibers are immersed in boiling water. However, γ phase crystal of PA6 remains unchanged in boiling water. Thus, β and γ phase crystals of PA6 can be differentiated by the crystalline behaviors of PA6 fibers after treatment in boiling water. Further experiments demonstrate that the β phase can also be produced during a drawing process where a phase transformation from γ to α occurs. In other words, β phase may act as an intermediate state during the phase transformation. [ABSTRACT FROM AUTHOR]

Free-float bike-sharing (FFBS) systems have increased in popularity as a sustainable travel mode in recent years, especially in the urban areas of China. Despite the convenience such systems offer to customers, it is not easy to maintain an effective balance in the distribution of bikes. This study considers the dynamic rebalancing problem for FFBS systems, whereby user-based tactics are employed by incentivizing users to perform repositioning activities. Motivated by the fact that the problem is frequently faced by FFBS system operators entering a new market with limited information on travel demand, we adopt the ranking and selection approach to select the optimal incentive plan. We describe the system dynamics in detail, and formulate a profit maximization problem with a constraint on customer service level. Through numerical studies, we first establish that our procedure can select the optimal incentive plan in a wide range of scenarios. Second, under our incentive plan, the profit and service level can be improved significantly compared with the scenario without incentive provision. Third, in most cases, our procedure can achieve the optimal solution with a reasonable sample size. [ABSTRACT FROM AUTHOR]