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An Iterative Procurement Combinatorial Auction Mechanism for the Multi-Item, Multi-Sourcing Supplier-Selection and Order-Allocation Problem under a Flexible Bidding Language and Price-Sensitive Demand
(2024-07-17) Abbaas, Omar; Ventura, Jose A.
This study addresses the multi-item, multi-sourcing supplier-selection and order-allocation problem. We propose an iterative procurement combinatorial auction mechanism that aims to reveal the suppliers’ minimum acceptable selling prices and assign orders optimally. Suppliers use a flexible bidding language to submit procurement bids. The buyer solves a Mixed Integer Non-linear Programming (MINLP) model to determine the winning bids for the current auction iteration. We introduce a buyer’s profit-improvement factor that constrains the suppliers to reduce their selling prices in subsequent bids. Moreover, this factor enables the buyer to strike a balance between computational effort and optimality gap. We develop a separate MINLP model for updating the suppliers’ bids while satisfying the buyer’s profit-improvement constraint. If none of the suppliers can find a feasible solution, the buyer reduces the profit-improvement factor until a pre-determined threshold is reached. A randomly generated numerical example is used to illustrate the proposed mechanism. In this example, the buyer’s profit improved by as much as 118% compared to a single-round auction. The experimental results show that the proposed mechanism is most effective in competitive environments with several suppliers and comparable costs. These results reinforce the importance of fostering competition and diversification in a supply chain.
The Effects of Mental Fatigue on Anaerobic Power and Power Endurance Performance
(2024-07-16) Gonzalez, Matthew P.; Brown, Denver M. Y.; Swafford, Isabella M.; Summerville, Bryce; Seidi, Morteza; Hajiaghamemar, Marzieh; Dorgo, Sandor
Mental fatigue has been studied extensively in relation to its impact on aerobic-, strength-, and motor-based tasks, but anaerobic power-based tasks have received limited attention. Interdisciplinary research investigating the underlying mechanisms by which mental fatigue influences physical performance has been called for. In two studies, the effects of mental fatigue on maximal power jump and endurance jump performance as well as kinetics and kinematics during jump performance were examined. Samples of collegiate volleyball players (Study 1; N = 14) and recreationally active students (Study 2; N = 27) completed two 30 min experimental manipulations (high vs. low cognitive control exertion) before performing three maximal power squat jumps followed by 15 repeated countermovement jumps, with measurements of kinetics and kinematics. For Study 1, the maximal power performance was significantly lower under a mentally fatigued condition, but no differences were observed for repeated jump performance, which may have been attributable to alterations in jump mechanics. For Study 2, no between-condition differences were observed for the maximal power performance, although repeated jump performance was significantly lower under a mentally fatigued condition. Collectively, these findings suggest that the impacts of mental fatigue on power-based performance tasks may depend on the task demands as well as the training status of the individual.
Analysis of the Skin and Brain Transcriptome of Normally Pigmented and Pseudo-Albino Southern Flounder (Paralichthys lethostigma) Juveniles to Study the Molecular Mechanisms of Hypopigmentation and Its Implications for Species Survival in the Natural Environment
(2024-07-16) Blandon, Ivonne R.; DiBona, Elizabeth; Battenhouse, Anna; Vargas, Sean; Mace, Christopher; Seemann, Frauke
Southern flounder skin pigmentation is a critical phenotypic characteristic for this species’ survival in the natural environment. Normal pigmentation allows rapid changes of color for concealment to capture prey and UV light protection. In contrast, highly visible hypopigmented pseudo-albinos exhibit a compromised immune system and are vulnerable to predation, sensitive to UV exposure, and likely have poor survival in the wild. Skin and brain tissue samples from normally pigmented and hypopigmented individuals were analyzed with next-generation RNA sequencing. A total of 1,589,613 transcripts were used to identify 952,825 genes to assemble a de novo transcriptome, with 99.43% of genes mapped to the assembly. Differential gene expression and gene enrichment analysis of contrasting tissues and phenotypes revealed that pseudo-albino individuals appeared more susceptible to environmental stress, UV light exposure, hypoxia, and osmotic stress. The pseudo-albinos’ restricted immune response showed upregulated genes linked to cancer development, signaling and response, skin tissue formation, regeneration, and healing. The data indicate that a modified skin collagen structure likely affects melanocyte differentiation and distribution, generating the pseudo-albino phenotype. In addition, the comparison of the brain transcriptome revealed changes in myelination and melanocyte stem cell activity, which may indicate modified brain function, reduced melanocyte migration, and impaired vision.
Stakeholders’ Perceptions on the Implementation of the HPV Vaccine School-Entry Requirement in Puerto Rico during the COVID-19 Pandemic
(2024-07-10) Vázquez-Otero, Coralia; Medina-Laabes, Diana T.; Pérez-Guzmán, Derick; Díaz-Miranda, Olga L.; Mercado-Andino, Alondra K.; Escabí-Wojna, Erika I.; Colón-López, Vivian
This study explored the implementation of the human papillomavirus (HPV) vaccine school-entry requirement in Puerto Rico during the COVID-19 pandemic. We conducted 26 semi-structured interviews with stakeholders and community-based organizations from August 2021 to March 2022. The interview guide was developed using the 2009 Consolidated Framework for Implementation Research (CFIR). The interviews were recorded and transcribed in Spanish. Data were analyzed using applied thematic techniques. These themes included the following: (i) Intervention characteristics: Participants noted that the school-entry requirement was effective in increasing vaccination uptake prior to the pandemic. Issues with the immunization registry were noted; (ii) Outer setting: External influences, access barriers, and an increase in HPV vaccine exemptions since the implementation of the COVID-19 vaccine were discussed; (iii) Inner setting: Communication within organizations and HPV vaccination efforts improved as the pandemic progressed; (iv) Characteristics of individuals: Most agreed with the school-entry requirement, including exemptions; and (v) Process: Results showed the need to reinforce the population’s education about HPV and the vaccine. Implementation of the policy was challenging during the early stages of the pandemic due to measures enacted to stop the spread of COVID-19 and focus on the COVID-19 vaccine. Efforts to increase HPV vaccine should focus on increasing HPV vaccine education and creating collaborations.
Racial Micro-Affirmations: Latinx Close Friendships and Ethnic Identity Development
(2024-07-05) Mireles-Rios, Rebeca; Garcia, Nichole Margarita; Castro, Isaac M. J.; Hernandez, Monica; Cerda, Rodolfo
Through analysis of semi-structured interviews of 30 Latinx college students, we examined how Latinx students experience belonging, acceptance, and affirmations at a Hispanic-Serving Research Institution (HSRI) in California. Drawing from the theoretical perspectives of racial micro-affirmations, we uncovered two major themes: the importance of close friendships and the impact that ethnic studies courses have on ethnoracial identity development. This study contributes to the ongoing discussion of the on-campus experiences of underrepresented students as well as how to best serve and affirm them at HSRIs.