1,124 research outputs found
Reinforcement Learning in Modern Biostatistics: Constructing Optimal Adaptive Interventions
Get PDFIn recent years, reinforcement learning (RL) has acquired a prominent position in health-related sequential decision-making problems, gaining traction as a valuable tool for delivering adaptive interventions (AIs). However, in part due to a poor synergy between the methodological and the applied communities, its real-life application is still limited and its potential is still to be realized. To address this gap, our work provides the first unified technical survey on RL methods, complemented with case studies, for constructing various types of AIs in healthcare. In particular, using the common methodological umbrella of RL, we bridge two seemingly different AI domains, dynamic treatment regimes and just-in-time adaptive interventions in mobile health, highlighting similarities and differences between them and discussing the implications of using RL. Open problems and considerations for future research directions are outlined. Finally, we leverage our experience in designing case studies in both areas to showcase the significant collaborative opportunities between statistical, RL, and healthcare researchers in advancing AIs.57 page
sj-pdf-1-smm-10.1177_09622802231188513 - Supplemental material for A flexible micro-randomized trial design and sample size considerations
No full textSupplemental material, sj-pdf-1-smm-10.1177_09622802231188513 for A flexible micro-randomized trial design and sample size considerations by Jing Xu, Xiaoxi Yan, Caroline Figueroa, Joseph Jay Williams and Bibhas Chakraborty in Statistical Methods in Medical Research</p
Corrigendum: Planning for livelihoods under hydrosocial uncertainty in periurban Pune(Front. Water, (2022), 4, (831464), 10.3389/frwa.2022.831464)
No full textIn the published article, there was an error in the author list, and authors “Sharlene L. Gomes, Shreya Chakraborty, and Leon M. Hermans” were erroneously excluded. The corrected author list appears below. “Sarah Luft Faculty of Mathematics and Natural Sciences, Institute for Geography, University of Cologne, Cologne, Germany Sharlene L. Gomes Faculty of Governance and Global Affairs, Institute of Public Administration, Leiden University, The Hague, Netherlands Shreya Chakraborty South Asia Consortium for Interdisciplinary Water Resources Studies, Hyderabad, India Leon M. Hermans Faculty of Technology, Policy, and Management, Delft University of Technology, Delft, Netherlands and Land andWaterManagement Department, IHE Delft Institute forWater Education, Delft, Netherlands.Policy Analysi
Adaptive learning algorithms to optimize mobile applications for behavioral health: guidelines for design decisions
Get PDFProviding behavioral health interventions via smartphones allows these interventions to be adapted to the changing behavior, preferences, and needs of individuals. This can be achieved through reinforcement learning (RL), a sub-area of machine learning. However, many challenges could affect the effectiveness of these algorithms in the real world. We provide guidelines for decision-making.
Using thematic analysis, we describe challenges, considerations, and solutions for algorithm design decisions in a collaboration between health services researchers, clinicians, and data scientists. We use the design process of an RL algorithm for a mobile health study "DIAMANTE" for increasing physical activity in underserved patients with diabetes and depression. Over the 1.5-year project, we kept track of the research process using collaborative cloud Google Documents, Whatsapp messenger, and video teleconferencing. We discussed, categorized, and coded critical challenges. We grouped challenges to create thematic topic process domains.
Nine challenges emerged, which we divided into 3 major themes: 1. Choosing the model for decision-making, including appropriate contextual and reward variables; 2. Data handling/collection, such as how to deal with missing or incorrect data in real-time; 3. Weighing the algorithm performance vs effectiveness/implementation in real-world settings.
The creation of effective behavioral health interventions does not depend only on final algorithm performance. Many decisions in the real world are necessary to formulate the design of problem parameters to which an algorithm is applied. Researchers must document and evaulate these considerations and decisions before and during the intervention period, to increase transparency, accountability, and reproducibility.
clinicaltrials.gov, NCT03490253.
© The Author(s) 2021. Published by Oxford University Press on behalf of the American Medical Informatics Association. All rights reserved. For permissions, please email: [email protected]
Fovea-Sparing Internal Limiting Membrane (ILM) Peeling and ILM Plug: A Novel Approach for Managing Optic Disc Pit Maculopathy
Get PDFSomnath Chakraborty,1 Jay Umed Sheth2 1Department of Vitreoretinal Services, Retina Institute of Bengal, Siliguri, India; 2Department of Vitreoretinal Services, Shantilal Shanghvi Eye Institute, Mumbai, Maharashtra, IndiaCorrespondence: Somnath Chakraborty, Department of Vitreoretinal Services, Retina Institute of Bengal, Siliguri, West Bengal, India, Email [email protected]: To evaluate the efficacy of fovea-sparing internal limiting membrane (ILM) peeling combined with ILM plug placement in patients with optic disc pit maculopathy (ODP-M).Patients and Methods: This retrospective study included seven eyes from seven patients diagnosed with ODP-M, treated with fovea-sparing ILM peeling and ILM plug placement. All patients underwent pars plana vitrectomy (PPV), with either SF6 gas or silicone oil used as tamponade. Outcome measures included best-corrected visual acuity (BCVA), central macular thickness (CMT), retinal reattachment, and resolution of retinoschitic lesions (RL). Data were collected at baseline and during follow-ups at 1, 3, 6, and 12 months.Results: The mean age of the study patients was 31 (± 13.14) years, with a marginal male preponderance (M: F = 4:3). All patients achieved complete retinal reattachment, with a significant reduction in CMT from 503.57 (± 154.74) μm preoperatively to 286.29 (± 22.43) μm at 12 months (P=0.02). BCVA improved in 85.7% of patients, from a mean of 0.77 (± 0.19) logMAR to 0.5 (± 0.25) logMAR by 12 months, though this was not statistically significant (P=0.27). Complete resolution of RL was observed in 71.4% of eyes, while 2 eyes showed partial resolution. One patient developed retinal detachment postoperatively, which was successfully managed with additional surgery.Conclusion: Fovea-sparing ILM peeling combined with ILM plug placement resulted in favorable anatomical and functional outcomes for ODP-M patients, with a 100% retinal reattachment rate and significant CMT reduction. This technique offers a viable alternative to conventional approaches, preserving foveal architecture while providing a mechanical barrier to fluid accumulation.Keywords: optic disc pit, optic disc pit maculopathy, fovea-sparing, internal limiting membrane peeling, vitrectom
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Daily Motivational Text Messages to Promote Physical Activity in University Students: Results From a Microrandomized Trial
Get PDFBackgroundLow physical activity is an important risk factor for common physical and mental disorders. Physical activity interventions delivered via smartphones can help users maintain and increase physical activity, but outcomes have been mixed.PurposeHere we assessed the effects of sending daily motivational and feedback text messages in a microrandomized clinical trial on changes in physical activity from one day to the next in a student population.MethodsWe included 93 participants who used a physical activity app, "DIAMANTE" for a period of 6 weeks. Every day, their phone pedometer passively tracked participants' steps. They were microrandomized to receive different types of motivational messages, based on a cognitive-behavioral framework, and feedback on their steps. We used generalized estimation equation models to test the effectiveness of feedback and motivational messages on changes in steps from one day to the next.ResultsSending any versus no text message initially resulted in an increase in daily steps (729 steps, p = .012), but this effect decreased over time. A multivariate analysis evaluating each text message category separately showed that the initial positive effect was driven by the motivational messages though the effect was small and trend-wise significant (717 steps; p = .083), but not the feedback messages (-276 steps, p = .4).ConclusionSending motivational physical activity text messages based on a cognitive-behavioral framework may have a positive effect on increasing steps, but this decreases with time. Further work is needed to examine using personalization and contextualization to improve the efficacy of text-messaging interventions on physical activity outcomes.Clinicaltrials.gov identifierNCT04440553
Comparative Analysis of Intravitreal Dexamethasone Implant (Ozurdex) and Brolucizumab Injection in the Treatment of Diabetic Macular Edema with Hyperreflective Intraretinal Dots: A Retrospective Study
Get PDFSomnath Chakraborty,1 Jay Umed Sheth2 1Department of Vitreoretinal Services, Retina Institute of Bengal, Siliguri, West Bengal, India; 2Department of Vitreoretinal Services, Shantilal Shanghvi Eye Institute, Mumbai, Maharashtra, IndiaCorrespondence: Somnath Chakraborty, Senior Consultant, Department of Vitreoretinal Services, Retina Institute of Bengal, Siliguri, West Bengal, India, Email [email protected]: This retrospective study aimed to compare the efficacy and safety of intravitreal Dexamethasone Implant (DEX) and Brolucizumab Injection in treating Diabetic Macular Edema (DME) with Hyperreflective Intraretinal Dots (HRID).Patients and Methods: A single-center retrospective study in India included 40 eyes (20 per group) with controlled diabetes and HRID on optical coherence tomography. Patients received either DEX or Brolucizumab, with outcomes assessed at various intervals up to 24 weeks. Primary measures included Best-Corrected Visual Acuity (BCVA), Central Macular Thickness (CMT), and safety parameters.Results: Both treatment groups demonstrated comparable baseline characteristics. Both treatments significantly improved the BCVA at weeks 4, 12, and 24, with the DEX implant showing significantly better results at week 12 than brolucizumab (P=0.04). In treatment-naïve eyes, BCVA improvements were similar across all time points. In recalcitrant DME eyes, DEX showed significant BCVA improvements at all time points, while brolucizumab showed significant improvements only at weeks 4 (P=0.005) and 24 (P=0.04). The CMT also improved with both treatments, with DEX showing superior reduction at weeks 4 (P=0.003), 12 (P=0.003), and 24 (P=0.002) respectively. In treatment-naïve eyes, DEX showed consistently better CMT reductions. In refractory DME eyes, both treatments significantly reduced CMT, with DEX performing better at week 12 (P=0.042). DEX required fewer injections (DEX: 1.5± 0.61; brolucizumab: 2.4± 0.82; P=0.0002) and less supplementary laser treatment (DEX:8/20, 40% eyes; brolucizumab: 16/20, 80%; P=0.01) compared to brolucizumab. No adverse events were observed in either group.Conclusion: The study suggests the potential superiority of intravitreal DEX implant over brolucizumab in managing DME with HRID. DEX exhibited sustained positive responses in BCVA and CMT, requiring fewer injections and supplementary interventions. Future research should explore extended follow-up durations, personalized treatment strategies, and refined biomarkers to optimize DME management.Keywords: diabetic macular edema, dexamethasone implant, Ozurdex, brolucizumab, hyperreflective intraretinal dot
Efficacy and Safety of an Indian Bevacizumab BIOSimilar (BEVATAS) for Retinal Vein Occlusion (BIOS-RVO Study)
Get PDFSomnath Chakraborty,1 Jay Umed Sheth2 1Department of Vitreoretinal Services, Retina Institute of Bengal, Siliguri, India; 2Department of Vitreoretinal Services, Shantilal Shanghvi Eye Institute, Mumbai, Maharashtra, IndiaCorrespondence: Somnath Chakraborty, Department of Vitreoretinal Services, Retina Institute of Bengal, Siliguri, West Bengal, India, Email [email protected]: To evaluate the efficacy and safety of Bevatas®, an Indian bevacizumab biosimilar, in the management of both Central Retinal Vein Occlusion (CRVO) and Branch Retinal Vein Occlusion (BRVO) (BIOS-RVO).Patients and Methods: The BIOS-RVO study was a retrospective interventional study conducted at a single tertiary eye care facility in India. 154 treatment-naïve eyes with RVO (CRVO: 62 eyes; BRVO: 92 eyes) received intravitreal bevacizumab biosimilar (IVBb) therapy. Data on best-corrected visual acuity (BCVA), central macular thickness (CMT), and intraocular pressure (IOP) were collected at baseline and at 3, 6, and 12 months post-therapy.Results: The average age of participants was approximately 55.99 (+ 12.56) years, with a nearly equal gender distribution (M:F = 49.4:50.6). Age differences between BRVO and CRVO groups were not significant (P=0.501), but gender distribution varied significantly (P=0.035), with more males in the CRVO group. Significant improvements in BCVA were observed in both CRVO and BRVO groups at 3 months, 6 months, and 1 year compared to baseline (P< 0.001). Both groups showed significant reductions in CMT throughout the follow-up period (P< 0.001). The mean number of injections was higher in the CRVO group (5.27[± 1.45]) compared to the BRVO group (4.27 [± 1.28]) (P< 0.001). Significant IOP increases were observed at 1 month (P< 0.001) and 6 months (P< 0.001) in both BRVO and CRVO groups, although not clinically significant. Safety analysis revealed no additional ocular or systemic adverse events during the study period.Conclusion: The BIOS-RVO study demonstrates that Bevatas is an effective and safe treatment option for both CRVO and BRVO. These findings support the use of Bevatas as a cost-effective alternative to branded anti-VEGF agents, particularly in resource-limited settings.Keywords: retinal vein occlusion, bevacizumab, biosimilar, Bevata
Electronic characterization of mass-selected acyclic, polycyclic and oxygenated hydrocarbons in neon matrices
Get PDFInterstellar chemistry embarked with the discovery of CH, CH+, and CN in extraterrestrial clouds. Presently, a large number of molecules have been identified in different galactic environments mostly by millimeter-wave and infrared spectroscopy. Molecular complexity and the spectral features dramatically depend on the particle density and the temperature of the astronomical region where they reside. Hence, spectroscopic analysis of extraterrestrial molecules has a valid mean to probe the physical and chemical condition and history of galactic media.
Life on Earth is carbon based and surprisingly, similar tendency has been found in interstellar molecules. Almost 80 percent of detected species contain carbon as a major constituent. Hence, a better characterization of the molecular universe may elucidate the origin of terrestrial life.
Two long standing riddles in molecular astrophysics are the diffuse interstellar absorption lines in the visible and the broad emission features in the mid-infrared. Carbonaceous systems ranging from small acyclic to polycyclic aromatics are considered to be the carriers of these absorption and emission bands. To recognize individual molecules responsible for these transitions, spectroscopic analysis of astrophysically relevant species in the laboratory is needed; comparison studies between astronomical measurements and laboratory spectra are the way for identification. These exotic molecules may be stable in galactic clouds under very cold and low density conditions but are extremely short-lived in the laboratory framework. Therefore, noncontemporary synthesizing and sensitive characterizing methods are required.
The matrix isolation spectroscopy is considered as an outdated-technique after the discovery of laser-based experiments but in combination with theory, it still serves a pivotal role in characterization of transient species. Exotic organics are synthesized in electrical discharge for the respective precursors. The ions of interest are co-deposited with neon on a cold surface (6 K) after mass-selection. Neutrals are generated in the matrix by UV irradiation.
The acyclic unsaturated organics possess very unique structural flexibility. By mass selective deposition of a particular m/z ratio in solid neon, several isomers have been detected. An advantage of the matrix isolation technique is that all possible electronic transitions of trapped species in the experimental measurement range can be recorded at once. Rare gases provide an environment in which the guest-host interactions slightly perturb the experimental band positions as compared to the gas-phase. Still matrix isolated spectrum is a good starting point for high resolution study and thence astrophysical findings.
Moderately intense absorptions are observed both in the visible and UV for C7Hn+/0 and C5Hn+/0, and charged oxygen containing polycarbon chains H2C6O+, HC7O+, and C4O2+ in neon matrices. The structural assignments of the electronic systems have been made on the basis of calculated ground-state stabilities with DFT and MP2 level of theory and computed excitation energies with TD DFT, SAC-CI, and CASPT2 methods. However, some of these ions and radicals have strong possibility to be the carriers of diffuse interstellar bands. The neutral oxygenated hydrocarbons are excluded as the carriers because no transition was detected after irradiation of the matrix. Theory explains that they possess strong transition in the deep UV. In addition, protonated PAHs and their oxygen containing analogs, which are credited for unidentified emission features, have been studied. Strong optical transitions suggest that they could be carriers of diffuse interstellar bands as well. A key species in combustion chemistry likely responsible for PAHs formation via mass-growth processes, fulvenallenyl radical, has been electronically characterized.
A part of this dissertation is devoted to physical organic chemistry. Reaction intermediates are too short-lived to probe. Nevertheless, identification of these species helps to infer a probable synthetic mechanism. Vibrationally resolved electronic spectra of fluorenylium, phenalenylium and fluorenyl radical have been measured in a neon matrix.
This electronic transition database of transient molecules created in the thesis can be used for their further gas-phase analysis and in situ detection in reaction or combustion systems
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