Browsing by Author "Chen, Yu"

Now showing 1 - 6 of 6
  • Thumbnail Image
    Item
    The Associative-Skew Clock Routing Problem
    (IEEE, 1999-11) Chen, Yu; Kahng, Andrew B.; Qu, Gang; Zelikovsky, Alexander
    We introduce the associative skew clock routing problem, which seeks a clock routing tree such that zero skew is preserved only within identified groups of sinks. The associative skew problem is easier to address within current EDA frameworks than useful-skew (skew-scheduling) approaches, and defines an interesting tradeoff between the traditional zero-skew clock routing problem (one sink group) and the Steiner minimum tree problem (n sink groups). We present a set of heuristic building blocks, including an efficient and optimal method of merging two zero-skew trees such that zero skew is preserved within the sink sets of each tree. Finally, we list a number of open issues for research and practical application.
  • Thumbnail Image
    Item
    Development of an Endoscopic Auto-Fluorescent Sensing Device to Aid in the Detection of Breast Cancer and Inform Photodynamic Therapy
    (MDPI, 2022-11-11) Gaitan, Brandon; Inglut, Collin; Kanniyappan, Udayakumar; Xu, He N.; Conant, Emily F.; Frankle, Lucas; Li, Lin Z.; Chen, Yu; Huang, Huang-Chiao
    Breast cancer is the most diagnosed cancer type in women, with it being the second most deadly cancer in terms of total yearly mortality. Due to the prevalence of this disease, better methods are needed for both detection and treatment. Reduced nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) are autofluorescent biomarkers that lend insight into cell and tissue metabolism. As such, we developed an endoscopic device to measure these metabolites in tissue to differentiate between malignant tumors and normal tissue. We performed initial validations in liquid phantoms as well as compared to a previously validated redox imaging system. We also imaged ex vivo tissue samples after modulation with carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP) and a combination of rotenone and antimycin A. We then imaged the rim and the core of MDA-MB-231 breast cancer tumors, with our results showing that the core of a cancerous lesion has a significantly higher optical redox ratio ([FAD]/([FAD] + [NADH])) than the rim, which agrees with previously published results. The mouse muscle tissues exhibited a significantly lower FAD, higher NADH, and lower redox ratio compared to the tumor core or rim. We also used the endoscope to measure NADH and FAD after photodynamic therapy treatment, a light-activated treatment methodology. Our results found that the NADH signal increases in the malignancy rim and core, while the core of cancers demonstrated a significant increase in the FAD signal.
  • Thumbnail Image
    Item
    Mother-child and father-child "serve and return" interactions at 9 months: Associations with children's language skills at 18, 24, and 30 months
    (2023) Chen, Yu; Cabrera, Natasha J; Human Development; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Infants learn language through the back-and-forth interactions with their parents where they “serve” by vocalizing, gesturing, or looking and parents “return” in a temporally and semantically contingent way. My dissertation focuses on these “serve and return” (SR) interactions between 9-month-old infants and their mothers and fathers (n = 296 parents and 148 infants) from ethnically and socioeconomically diverse backgrounds by examining the variability in SR interactions explained by maternal and paternal psychological distress, the association between SR interactions and children’s language skills at 18, 24, and 30 months, and the moderation effect of maternal and paternal SR interactions on language outcomes. Psychological distress was indicated by parent-reported depressive symptoms, parenting stress, and role overload, and SR interactions were transcribed and coded from video-taped parent-child toy play activities during home visits. I report three major findings. First, neither maternal nor paternal psychological distress was significantly associated with and SR interactions at 9 months, controlling for demographic factors. Second, fathers who responded to their child’s serves more promptly and mothers who provided more semantically relevant responses had children with higher receptive and expressive language skills, respectively, at 18 and 30 months. Third, fathers’ semantically relevant responses were negatively associated with children’s receptive language skills at 24 months; however, this main effect was moderated by mothers’ semantically relevant responses. Understanding how mothers and fathers engage in temporally and semantically contingent social interactions with their children during the first year, especially among families from diverse backgrounds, would enable programs and policies to more effectively promote early language development and reduce gaps in school readiness.
  • Thumbnail Image
    Item
    Quantifying the Photochemical Damage Potential of Contrast-Enhanced Fluorescence Imaging Products: Singlet Oxygen Production
    (Wiley, 2022-04-20) Gaitan, Brandon; Frankle, Lucas; Vig, Shruti; Oskoui, Ellen; Adwan, Miriam; Chen, Yu; Elespuru, Rosalie; Huang, Huang-Chiao; Pfefer, T. Joshua
    The benefits of contrast-enhancing imaging probes have become apparent over the past decade. However, there is a gap in the literature when it comes to the assessment of the phototoxic potential of imaging probes and systems emitting visible and/or near-infrared radiation. The primary mechanism of fluorescent agent phototoxicity is thought to involve the production of reactive molecular species (RMS), yet little has been published on the best practices for safety evaluation of RMS production levels for clinical products. We have proposed methods involving a cell-free assay to quantify singlet oxygen [(SO) a known RMS] generation of imaging probes, and performed testing of Indocyanine Green (ICG), Proflavine, Methylene Blue, IR700 and IR800 at clinically relevant concentrations and radiant exposures. Results indicated that SO production from IR800 and ICG were more than two orders of magnitude below that of the known SO generator Rose Bengal. Methylene Blue and IR700 produced much higher SO levels than ICG and IR800. These results were in good agreement with data from the literature. While agents that exhibit spectral overlap with the assay may be more prone to errors, our tests for one of these agents (Proflavine) appeared robust. Overall, our results indicate that this methodology shows promise for assessing the phototoxic potential of fluorophores due to SO production.
  • Thumbnail Image
    Item
    Risks and Protective Factors of Hispanic Families and Their Young Children during the COVID-19 Pandemic
    (MDPI, 2022-05-27) Cabrera, Natasha; He, Minxuan; Chen, Yu; Reich, Stephanie M.
    This study examines the risk-related factors during the pandemic and protective factors that might reduce its effects on family functioning in a sample of 161 low-income Hispanic parents in the United States, recruited from an ongoing longitudinal intervention study. They were surveyed about family functioning six months into the pandemic. We focused on the associations between social (e.g., exposure to the virus) and economic (e.g., job loss) pandemic-related risks on parental stress, parenting, and children’s socioemotional problems and skills, as well as the degree to which coparenting support, parents’ positivity, economic support, and access to services and information mitigated (protected) the negative effects of these stressors on family functioning. We found that increases in economic risk were associated with more child competence skills, whereas increases in social risk were associated with less parental engagement. Positivity and economic support moderated the effects of economic risk on parental stress and engagement. These findings show that to intervene effectively with low-income Hispanic families, we need to strengthen and support the resources for coping with adversity.
  • Thumbnail Image
    Item
    Test method for evaluating the photocytotoxic potential of fluorescence imaging products
    (Wiley, 2023-07-26) Vig, Shruti; Gaitan, Brandon; Frankle, Lucas; Chen, Yu; Elespuru, Rosalie; Pfefer, T. Joshua; Huang, Huang-Chiao
    Various fluorescence imaging agents are currently under clinical studies. Despite significant benefits, phototoxicity is a barrier to the clinical translation of fluorophores. Current regulatory guidelines on medication-based phototoxicity focus on skin effects during sun exposure. However, with systemic and local administration of fluorophores and targeted illumination, there is now possibility of photochemical damage to deeper tissues during intraoperative imaging procedures. Hence, independent knowledge regarding phototoxicity is required to facilitate the development of fluorescence imaging products. Previously, we studied a cell-free assay for initial screening of reactive molecular species generation from fluorophores. The current work addresses a safety test method based on cell viability as an adjunct and a comparator with the cell-free assay. Our goal is to modify and implement an approach based on the in vitro 3T3 neutral red uptake assay of the Organization for Economic Co-Operation and Development Test Guideline 432 (OECD TG432) to evaluate the photocytotoxicity of clinically relevant fluorophores. These included indocyanine green (ICG), proflavine, methylene blue (MB), and IRDye800, as well as control photosensitizers, benzoporphyrin derivative (BPD) and rose bengal (RB). We performed measurements at agent concentrations and illumination parameters used for clinic imaging. Our results aligned with prior studies, indicating photocytotoxicity in RB and BPD and an absence of reactivity for ICG and IRDye800. DNA interactive agents, proflavine and MB, exhibited drug/light dose–response curves like photosensitizers. This study provides evidence and insights into practices useful for testing the photochemical safety of fluorescence imaging products.