Duke University
  • Durham, North Carolina, United States
Recent publications
Background: Clinicians are often familiar with quality improvement (QI) and evidence-based practice (EBP) processes, which provides guidance into what evidence should be implemented; however, these processes do not address how to successfully implement evidence. Objective: Clinicians would benefit from a deeper understanding of implementation science, along with practical tools for how to use these principles in QI and EBP projects. Methods: We provide a brief background of the principles of implementation science, an overview of current implementation science models and a toolkit to facilitate choosing and using common implementation science strategies. In addition, the toolkit provides guidance for measuring the success of an implementation science project and a case study showing how implementation science strategies can be used successfully in clinical practice. Conclusions: Using an implementation science toolkit for designing, conducting, and evaluating a QI or EBP project improves the quality and generalizability of results.
Digital microfluidic biochips have emerged as a promising alternative for various laboratory procedures in biochemistry such as drug discovery and DNA sequencing. A recent generation of digital biochips uses a micro-electrode-dotarray (MEDA) architecture, which provides finer controllability of droplets and seamlessly integrates microelectronics and microfluidics. To simplify the wiring design of such biochips, all microelectrodes and their control registers are daisy-chained together. Therefore, the ability to both identify faults in the chain and tolerate them is required in MEDA biochips. In this study, a new daisy-chain design approach is proposed, integrating a built-in self-repair scheme that can automatically detect faults and correct them. Moreover, an efficient test generation method that requires only a small number of test vectors is proposed to achieve 100% fault coverage without degrading the electrodes. The proposed self-repair scheme can be used in both offline and online modes. Experimental results show that detection and repair can be carried out for various types of faults that can occur in daisy chains.
A large amount of high-dimensional and heterogeneous data appear in practical applications, which are often published to third parties for data analysis, recommendations, targeted advertising, and reliable predictions. However, publishing these data may disclose personal sensitive information, resulting in an increasing concern on privacy violations. Privacy-preserving data publishing has received considerable attention in recent years. Unfortunately, the differentially private publication of high dimensional data remains a challenging problem. In this paper, we propose a differentially private high-dimensional data publication mechanism (DP2-Pub) that runs in two phases: a Markov-blanket-based attribute clustering phase and an invariant post randomization (PRAM) phase. Specifically, splitting attributes into several low-dimensional clusters with high intra-cluster cohesion and low inter-cluster coupling helps obtain a reasonable allocation of privacy budget, while a double-perturbation mechanism satisfying local differential privacy facilitates an invariant PRAM to ensure no loss of statistical information and thus significantly preserves data utility. We also extend our DP2-Pub mechanism to the scenario with a semi-honest server which satisfies local differential privacy. We conduct extensive experiments on four real-world datasets and the experimental results demonstrate that our mechanism can significantly improve the data utility of the published data while satisfying differential privacy.
Modular multilevel converters are well known in the energy sector. Generally, their stable operation is at the expense of numerous sensors, communication burden, and computationally expensive balancing strategies that challenge their expansion to cost-driven applications. Hence, introducing a sensorless voltage-balancing strategy with a simple controller is an attractive objective. Diode-clamped MMCs offer a simple and effective solution by providing a unidirectional balancing path between two modules through a diode. Ideally, the modulation technique should compensate for the lack of bidirectional energy transfer; hence open-loop operation is possible. Although the sensorless operation is desirable to reduce costs, good knowledge of the modules' voltages for system monitoring and protection functions still improves operation in some applications or is mandatory in others. However, information should not be at the cost of additional sensors and communication bandwidth. This paper develops a compensated state-space model for diode-clamped MMCs to estimate module voltages using an optimal estimator without any direct measurement at module levels. The model considers the effect of the diode-clamped branches and their balancing effect, resulting in 30% to 50% reduction in estimation error compared to the conventional models using similar estimators. Simulations and experiments further confirm the provided analysis, where the estimator achieves >97.5% accuracy.
KIF20A is a critical kinesin for cell division and a promising anti-cancer drug target. The mechanisms underlying its cellular roles remain elusive. Interestingly, unusual coupling between the nucleotide- and microtubule-binding sites of this kinesin-6 has been reported, but little is known about how its divergent sequence leads to atypical motility properties. We present here the first high-resolution structure of its motor domain that delineates the highly unusual structural features of this motor, including a long L6 insertion that integrates into the core of the motor domain and that drastically affects allostery and ATPase activity. Together with the high-resolution cryo-electron microscopy microtubule-bound KIF20A structure that reveals the microtubule-binding interface, we dissect the peculiarities of the KIF20A sequence that influence its mechanochemistry, leading to low motility compared to other kinesins. Structural and functional insights from the KIF20A pre-power stroke conformation highlight the role of extended insertions in shaping the motor's mechanochemical cycle. Essential for force production and processivity is the length of the neck linker in kinesins. We highlight here the role of the sequence preceding the neck linker in controlling its backward docking and show that a neck linker four times longer than that in kinesin-1 is required for the activity of this motor.
Gradient Boosting Machines (GBMs) have achieved remarkable success in effectively solving a wide range of problems by leveraging Taylor expansions in functional space. Second-order Taylor-based GBMs, such as XGBoost rooted in Newton's method, consistently yield state-of-the-art results in practical applications. However, it is important to note that the loss functions used in second-order GBMs must strictly adhere to convexity requirements, specifically requiring a positive definite Hessian of the loss. This restriction significantly narrows the range of objectives, thus limiting the application scenarios. In contrast, first-order GBMs are based on the first-order gradient optimization method, enabling them to handle a diverse range of loss functions. Nevertheless, their performance may not always meet expectations. To overcome this limitation, we introduce Trust-region Boosting (TRBoost), a new and versatile Gradient Boosting Machine that combines the strengths of second-order GBMs and the versatility of first-order GBMs. In each iteration, TRBoost employs a constrained quadratic model to approximate the objective and applies the Trust-region algorithm to obtain a new learner. Unlike GBMs based on Newton's method, TRBoost does not require a positive definite Hessian, enabling its application to more loss functions while achieving competitive performance similar to second-order algorithms. Convergence analysis and numerical experiments conducted in this study confirm that TRBoost exhibits similar versatility to first-order GBMs and delivers competitive results compared to second-order GBMs. Overall, TRBoost presents a promising approach that achieves a balance between performance and generality, rendering it a valuable addition to the toolkit of machine learning practitioners.
Background and Aims Recently, we demonstrated that a distinct pattern of structural covariance networks (SCN) from magnetic resonance imaging (MRI)‐derived measurements of brain cortical thickness characterized young adults with alcohol use disorder (AUD) and predicted current and future problematic drinking in adolescents relative to controls. Here, we establish the robustness and value of SCN for identifying heavy alcohol users in three additional independent studies. Design and Setting Cross‐sectional and longitudinal studies using data from the Pediatric Imaging, Neurocognition and Genetics (PING) study ( n = 400, age range = 14–22 years), the National Consortium on Alcohol and Neurodevelopment in Adolescence (NCANDA) ( n = 272, age range = 17–22 years) and the Human Connectome Project (HCP) ( n = 375, age range = 22–37 years). Cases Cases were defined based on heavy alcohol use patterns or former alcohol use disorder (AUD) diagnoses: 50, 68 and 61 cases were identified. Controls had none or low alcohol use or absence of AUD: 350, 204 and 314 controls were selected. Measurements Graph theory metrics of segregation and integration were used to summarize SCN. Findings Mirroring our prior findings, and across the three data sets, cases had a lower clustering coefficient [area under the curve (AUC) = −0.029, P = 0.002], lower modularity (AUC = −0.14, P = 0.004), lower average shortest path length (AUC = −0.078, P = 0.017) and higher global efficiency (AUC = 0.007, P = 0.010). Local efficiency differences were marginal (AUC = −0.017, P = 0.052). That is, cases exhibited lower network segregation and higher integration, suggesting that adjacent nodes (i.e. brain regions) were less similar in thickness whereas spatially distant nodes were more similar. Conclusion Structural covariance network (SCN) differences in the brain appear to constitute an early marker of heavy alcohol use in three new data sets and, more generally, demonstrate the utility of SCN‐derived metrics to detect brain‐related psychopathology.
Afrocentrism is a perspective wherein phenomena, ideas, events, and cultures that influence the lives of people of African descent are centered within the epistemologies of the African descent communities. Afrocentrism as a socialization mechanism for youth has been increasingly endorsed by African descent communities globally but remains nascent within youth studies literature on adolescent development. The omission of Afrocentrism as a perspective on youth development represents an oversight of culturally responsive, anti-racist research with African-descent youth populations. This conceptual article revisits Afrocentrism as a perspective to envision healthy development of Black youth. In doing so, the authors propose that positive development among Black youth intersects not only with the reality of youth developmental universalisms and race-related concerns, but also that Africanness and associated philosophical underpinnings, as will be described, are central to their healthy development. Historical, theoretical, and findings from exemplar Afrocentric programs are presented, with implications for future scholarship.
Out-of-school adolescent girls/young women (AGYW) in Africa are at increased risk for HIV and are underserved by HIV prevention interventions. Identifying social networks of out-of-school AGYW may be a strategic approach for reaching them. A sequential mixed methods study design was used. The PLACE (Priorities for Local AIDS Control Efforts) methodology, implemented in one ward of Dar es Salaam, Tanzania, identified 69 networks of AGYW. We randomly selected 28 networks and conducted surveys and network assessments with 80.9% (n = 310) of the members. On average, the networks consisted of 13.7 members, and had a density of 0.65 and a transitivity of 0.80, indicating high cohesion. The networks were mostly female (92%). On average, 67% of network membership were AGYW aged 15–24 years, of whom 70% were out-of-school and 67% were sexually active. Among sexually active AGYW aged 15–24, self-reported HIV seropositivity was 12.2%. We then conducted focus group discussions with 6 purposively selected networks. AGYW described their networks as sources of support and advice. Social norms supported AGYW engaging in transactional sex to alleviate life’s hardships; it was the easiest way to earn income without “sweating”. AGYW discussed IPV as a common experience, and social norms stigmatized AGYWs’ use of condoms. AGYW were largely unaware of pre-exposure prophylaxis. The self-reported HIV prevalence rates of this cohort were higher than national averages, suggesting we tapped into high-risk networks. Social norms promoted transactional and unprotected sex. Social networks are an acceptable channel for HIV prevention intervention delivery to out-of-school AGYW.
Purpose The number of articles retracted by peer-reviewed journals has increased in recent years. This study systematically reviews retracted publications in the spine surgery literature. Methods A search of PubMed MEDLINE, Ovid EMBASE, Retraction Watch, and the independent websites of 15 spine surgery-related journals from inception to September of 2022 was performed without language restrictions. PRISMA guidelines were followed with title/abstract screening, and full-text screening was conducted independently and in duplicate by two reviewers. Study characteristics and bibliometric information for each publication was extracted. Results Of 250 studies collected from the search, 65 met the inclusion criteria. The most common reason for retraction was data error (n = 15, 21.13%), followed by plagiarism (n = 14, 19.72%) and submission to another journal (n = 14, 19.72%). Most studies pertained to degenerative pathologies of the spine (n = 32, 80.00%). Most articles had no indication of retraction in their manuscript (n = 24, 36.92%), while others had a watermark or notice at the beginning of the article. The median number of citations per retracted publication was 10.0 (IQR 3–29), and the median 4-year impact factor of the journals was 5.05 (IQR 3.20–6.50). On multivariable linear regression, the difference in years from publication to retraction (p = 0.0343, β = 6.56, 95% CI 0.50–12.62) and the journal 4-year impact factor (p = 0.0029, β = 7.47, 95% CI 2.66–12.28) were positively associated with the total number of citations per retracted publication. Most articles originated from China (n = 30, 46.15%) followed by the United States (n = 12, 18.46%) and Germany (n = 3, 4.62%). The most common study design was retrospective cohort studies (n = 14, 21.54%). Conclusions The retraction of publications has increased in recent years in spine surgery. Researchers consulting this body of literature should remain vigilant. Institutions and journals should collaborate to increase publication transparency and scientific integrity.
Developmental theories suggest that exposure to early life adversity (ELA) alters developing emotional response systems, predicting risk for psychopathology across the life span. The present study examines whether negative emotionality (NE), a trait-like measure of emotionality that develops during early childhood, mediates the association between ELA and psychopathology in a representative sample of 917 preschoolers (Mage = 3.84). Additionally, we explored whether cognitive control, which supports attentional focusing and inhibition and has been identified as a transdiagnostic protective factor, moderates the impact of heightened emotionality following adversity on psychopathology risk. We utilized parent report of adversity, psychopathology, and NE and parent report and task-based measures of cognitive control. Structural equation modeling of cross-sectional data revealed that NE partially mediated the link between ELA and psychopathology symptoms. Moreover, parent-reported cognitive control buffered this link such that the effect of ELA on psychopathology through NE was stronger in children with low versus high cognitive control. These results identify elevated NE as one mechanism linking ELA and psychopathology, specifically among children with poorer top-down control, informing our understanding of key risk and protective factors among adversity-exposed children.
What motivates private firms’ willingness to invest in green technologies and environmentally friendly operations? Some emphasize enhanced government regulation and enforcement, while others point to the greater potential of societal pressure. In this study, we use a survey experiment with more than 10,000 firms in Vietnam to test which type of stakeholder pressure has the strongest impact on domestic and foreign business leaders’ intention to invest in green operations. We find that the effectiveness of stakeholder pressure is conditioned by the firms’ target markets. Foreign investors are more susceptible than domestic firms to intensive regulatory pressure. Accounting for export orientation, however, we find that the most amenable policy targets for regulatory pressure are foreign firms aiming to sell in the Vietnamese domestic market.
Magneto‐optical microscopies, including optical measurements of magnetic circular dichroism, are increasingly ubiquitous tools for probing spin‐orbit coupling, charge‐carrier g‐factors, and chiral excitations in matter, but the minimum detectable signal in classical magnetic circular dichroism measurements is fundamentally limited by the shot‐noise limit of the optical readout field. Here, a two‐mode squeezed light source is used to improve the minimum detectable signal in magnetic circular dichroism measurements by 3 decibels compared with state‐of‐the‐art classical measurements, even with relatively lossy samples like terbium gallium garnet. These results provide a framework for new quantum‐enhanced magneto‐optical microscopies that are particularly critical for environmentally sensitive materials and for low temperature measurements where increased optical power can introduce unacceptable thermal perturbations.
Parallel operations are important for both near‐term quantum computers and larger‐scale fault‐tolerant machines because they reduce execution time and qubit idling. This study proposes and implements a pairwise‐parallel gate scheme on a trapped‐ion quantum computer. The gates are driven simultaneously on different sets of orthogonal motional modes of a trapped‐ion chain. This work demonstrates the utility of this scheme by creating a Greenberger‐Horne‐Zeilinger (GHZ) state in one step using parallel gates with one overlapping qubit. It also shows its advantage for circuits by implementing a digital quantum simulation of the dynamics of an interacting spin system, the transverse‐field Ising model. This method effectively extends the available gate depth by up to two times with no overhead when no overlapping qubit is involved, apart from additional initial cooling. This scheme can be easily applied to different trapped‐ion qubits and gate schemes, broadly enhancing the capabilities of trapped‐ion quantum computers.
Objective This study aimed to evaluate whether there are genetic variants associated with adverse neurodevelopmental outcomes in extremely low birth weight (ELBW) infants. Study Design We conducted a candidate gene association study in two well-defined cohorts of ELBW infants (<1,000 g). One cohort was for discovery and the other for replication. The discovery case–control analysis utilized anonymized DNA samples and evaluated 1,614 single-nucleotide polymorphisms (SNPs) in 145 genes concentrated in inflammation, angiogenesis, brain development, and oxidation pathways. Cases were children who died by age one or who were diagnosed with cerebral palsy (CP) or neurodevelopmental delay (Bayley II mental developmental index [MDI] or psychomotor developmental index [PDI] < 70) by 18 to 22 months. Controls were survivors with normal neurodevelopment. We assessed significant epidemiological variables and SNPs associated with the combined outcome of CP or death, CP, mental delay (MDI < 70) and motor delay (PDI < 70). Multivariable analyses adjusted for gestational age at birth, small for gestational age, sex, antenatal corticosteroids, multiple gestation, racial admixture, and multiple comparisons. SNPs associated with adverse neurodevelopmental outcomes with p < 0.01 were selected for validation in the replication cohort. Successful replication was defined as p < 0.05 in the replication cohort. Results Of 1,013 infants analyzed (452 cases, 561 controls) in the discovery cohort, 917 were successfully genotyped for >90% of SNPs and passed quality metrics. After adjusting for covariates, 26 SNPs with p < 0.01 for one or more outcomes were selected for replication cohort validation, which included 362 infants (170 cases and 192 controls). A variant in SERPINE1, which encodes plasminogen activator inhibitor (PAI1), was associated with the combined outcome of CP or death in the discovery analysis (p = 4.1 × 10−4) and was significantly associated with CP or death in the replication cohort (adjusted odd ratio: 0.4; 95% confidence interval: 0.2–1.0; p = 0.039). Conclusion A genetic variant in SERPINE1, involved in inflammation and coagulation, is associated with CP or death among ELBW infants. Key Points
Problem definition: Guided delegation, a practice in which companies provide guidelines when delegating supplier management to tier 1 firms, is a common practice in managing complex supply chains. We study the benefits and risks of this approach in a three-tier supply chain setting consisting of a buying firm, a tier 1 contract manufacturer, and tier 2 suppliers, where responsibility risk stems from the tier 2 suppliers. We analyze the buyer’s profit and the supply chain’s responsibility risk under a guided-delegation model, in which the buyer specifies an authorized tier 2 supplier for the tier 1 manufacturer as a guideline and may audit the tier 1 firm for compliance. We compare this model with a full-delegation model, in which the buyer fully delegates tier 2 supplier selection to the tier 1 firm. Methodology/results: We formulate a Stackelberg game for the buyer’s contract design problem. We show that guided delegation does not always yield its expected results of lower supply chain risk and greater buyer profit. In instances where compliance auditing is financially more attractive to the buyer than paying a premium for tier 1’s responsible sourcing, guided delegation can result in higher profit but increased risk because compliance auditing cannot completely eliminate the risk. Additionally, when tier 1 anticipates buyer audits and demands higher wholesale prices to offset potential penalties, guided delegation may lead to decreased risk but lower profit for the buyer. Our analysis shows that delegating audit responsibilities to tier 1 often does not improve the buyer’s profit, and in situations where it does, it invariably raises the supply chain risk. Managerial implications: Our research identifies the potential downsides of guided delegation, offering insight for external stakeholders on where to focus efforts to avoid these pitfalls. It suggests that the intended benefits of guided delegation can only be realized when paired with compliance auditing. Supplemental Material: The online appendix is available at https://doi.org/10.1287/msom.2020.0446 .
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Brandon M Schickling
  • Department of Medicine
Zoe Jewell
  • Nicholas School of the Environment
Bill Seaman
  • Department of Art, Art History & Visual Studies
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