Interplay between multiple scattering, emission, and absorption of light in the phosphor of a white light-emitting diode

We study light transport in phosphor plates of white light-emitting diodes (LEDs). We measure the broadband diffuse transmission through phosphor plates of varying YAG:Ce$^{3+}$ density. We distinguish the spectral ranges where absorption, scattering, and re-emission dominate. Using diffusion theory, we derive the transport and absorption mean free paths from first principles. We find that both transport and absorption mean free paths are on the order of the plate thickness. This means that phosphors in commercial LEDs operate well within an intriguing albedo range around 0.7. We discuss how salient parameters that can be derived from first principles control the optical properties of a white LED.Comment: 14 pages, 9 figure

Analytical modeling of light transport in scattering materials with strong absorption

We have investigated the transport of light through slabs that both scatter and strongly absorb, a situation that occurs in diverse application fields ranging from biomedical optics, powder technology, to solid-state lighting. In particular, we study the transport of light in the visible wavelength range between $420$ and $700$ nm through silicone plates filled with YAG:Ce$^{3+}$ phosphor particles, that even re-emit absorbed light at different wavelengths. We measure the total transmission, the total reflection, and the ballistic transmission of light through these plates. We obtain average single particle properties namely the scattering cross-section $\sigma_s$, the absorption cross-section $\sigma_a$, and the anisotropy factor $\mu$ using an analytical approach, namely the P3 approximation to the radiative transfer equation. We verify the extracted transport parameters using Monte-Carlo simulations of the light transport. Our approach fully describes the light propagation in phosphor diffuser plates that are used in white LEDs and that reveal a strong absorption ($L/\ell_{\mathrm{a}} > 1$) up to $L/\ell_{\mathrm{a}} = 4$, where $L$ is the slab thickness, $\ell_{\mathrm{a}}$ is the absorption mean free path. In contrast, the widely used diffusion theory fails to describe this parameter range. Our approach is a suitable analytical tool for industry, since it provides a fast yet accurate determination of key transport parameters, and since it introduces predictive power into the design process of white light emitting diodes

PHP47 - Early assessment of highly innovative medical technology: clinical and economical gains of point-of-care applications for measuring potassium concentrations

OBJECTIVES:\ud Innovative point-of-care diagnostics are likely to be having a strong impact on health care. The aim of this study is to conduct an early assessment of point-of-care chips. These chips can detect many particles and, consequently, many product-market combinations can be developed. This study investigates the impact of potential point-of-care applications in health care and to quantify the impact in terms of their likely cost-effectiveness.\ud \ud METHODS:\ud The Analytic Hierarchy Process (AHP); a technique for multi-criteria analysis, and Markov modeling were applied in this early assessment. The AHP was used to prioritize six potentially attractive product-market combinations (PCM’s). For estimating the future cost-effectiveness of the most attractive PMC’s, Markov health state transition models were developed. Two Markov models were constructed; models for a potassium chip for both stage 5 CKD patients as well as heart failure (HF) patients which suffer from edemas.\ud \ud RESULTS:\ud AHP identified clinical gain as being the most important criterion to assess the attractiveness of a PMC, followed by market potential, attitude of professionals, R&D barriers and implementation barriers. Regarding these criteria, a potassium-chip for Chronic Kidney Disease (CKD) and Heart Failure (HF) patients was calculated to be the most attractive alternative. Markov model cohort simulation yielded incremental cost-effectiveness ratios (ICERs). The point-of-care chip appeared not to be cost-effective for preventing hyperkalemia in stage 5 CKD patients. For HF patients suffering from edemas the chip was estimated to be cost-effective and could provide a valuable asset to current treatment.\ud \ud CONCLUSIONS:\ud The AHP is valuable in supporting the identification of potentially attractive product-market combinations. For the best combinations, Markov modeling can subsequently provide a more in-depth analysis of the future cost-effectiveness

Modeling of Whole Genomic Sequencing Implementation using System Dynamics and Game Theory

Biomarker testing is a laboratory test in oncology that is used in the selection of targeted cancer treatments and helping to avoid ineffective treatments. There exist several types of biomarker tests that can be used to detect the presence of particular mutations or variation in gene expression. Whole Genome Sequencing (WGS) is a biomarker test for analyzing the entire genome. WGS can provide more comprehensive diagnostic information, but it is also more expensive than other tests. In this study, System Dynamics and Game Theoretic models are employed to evaluate scenarios, and facilitate organizational decision making regarding WGS implementation. These models evaluate the clinical and economic value of WGS as well as its affordability and accessibility. The evaluated scenarios have covered the timing of implementing WGS using time to diagnosis and total cost.Comment: The IISE Annual Conference & Expo 202

PDB73 – The Expected Value Of Bio-Artificial Pancreas Development In View Of Endocrinologists' And Patients' Preferences

Objectives Islet transplantation is an accepted transplantation method in type I Diabetes Mellitus, yet islet survival is hampered due to an insufficient transplantation site and severe immunological and inflammatory responses. The development of a bio-artificial pancreas (BAP) may contribute to transplanted islet functionality and survival. The objective of this study is to identify the most important transplantation characteristics and to asses patients’ and endocrinologists´ preferences for three potential BAP scenarios in order to guide further development. Methods The current standard of care and characteristics that determine clinical decisions for a particular transplantation method were analysed based on a literature search, semi-structured interviews and focus groups. A decision tree was constructed covering the main attributes effectiveness, patient safety, impact of the treatment for the patient and the required amount of donor material. The analytic hierarchy process was used to obtain the relative weights for each defined attribute in type I DM patients (n=21) and endocrinologists (n=12). Based on these weights, overall preferences for three potential BAP scenarios were calculated and compared to conventional pancreas and islets transplantation. Results The three most important treatment attributes are the effectiveness of the transplant for glucose control, patient safety and the surgical procedure. However, there were considerable differences between patients and endocrinologists in the importance of effectiveness of the transplant (weights were 0.471 and 0.257 respectively) and patient safety (0.331 and 0.423). While considering both endocrinologists’ and patients’ preferences, all three BAP scenarios assessed gained a higher overall preference in comparison to conventional islet transplantation. Conclusions This study indicates the prospects of BAP development. Nevertheless, the study also highlights the discrepancies between endocrinologists’ and type 1 diabetes patients’ preferences. In the future, BAP developers can benefit from this multidisciplinary approach by critically reviewing their BAP design, in view of patient safety and clinical performanc

Alternative computation of the Seidel aberration coefficients using the Lie algebraic method

We give a brief introduction to Hamiltonian optics and Lie algebraic methods. We use these methods to describe the operators governing light propagation, refraction, and reflection in phase space. The method offers a systematic way to find aberration coefficients of any order for arbitrary rotationally symmetric optical systems. The coefficients from the Lie method are linked to the Seidel aberration coefficients. Furthermore, the property of summing individual surface contributions is preserved by the Lie algebraic theory. Two examples are given to validate the proposed methodology with good results.</p

Health Economic Evidence and Modeling Challenges for Liquid Biopsy Assays in Cancer Management:A Systematic Literature Review

BACKGROUND: Cancer-derived material circulating in the bloodstream and other bodily fluids, referred to as liquid biopsies (LBs), has become an appealing adjunct or alternative to tissue biopsies, showing vital promise in several clinical applications.PURPOSE: A systematic literature review was conducted to (1) summarize the current health economic evidence for LB assays and (2) identify and analyze the studies addressed or reported on the challenges of health economic modeling in precision medicine.METHODS: Relevant studies were identified in the EMBASE, MEDLINE, Cochrane Library, EconLit, and the University of Melbourne Full Text Journal databases from 1 January 2013 to 16 September 2022. Included papers were selected if they were economic evaluations and/or budget impact analyses.RESULTS: A total of 24 studies were included and analyzed, with the majority being full economic evaluations (n = 19, 79.2%). Four studies (16.7%) were health and budget impact analyses, and one study (4.1%) incorporated both an economic evaluation and a budget impact analysis. Cohort-level modeling techniques were the most common approach (n = 16; 80%). LB technologies were cost-effective in 15 studies (75%) considering different biomarkers, cancer types and stages, and economic analyses. These studies evaluated LBs for screening and early detection (66.7%), treatment selection (26.7%), and monitoring treatment response (6.6%). Budget impact analysis results were varied among included studies, with the majority of studies (n = 4; 80%) reporting either cost savings, minimal, or modest budget impact, while one study (20%) reported LBs as an efficient strategy. The reviewed studies often inadequately reported or addressed modeling challenges, such as patient-level processes, the combination of tests and treatments, preferences, and uncertainty.CONCLUSION: LBs could provide a cost-effective approach for treatment selection in lung cancer and aid in the screening and early detection of other cancers, including colorectal, gastric, breast, and brain cancers. This is in comparison with various alternatives, such as the standard of care (SOC) and no screening scenario. However, it is important to mention that in some comparisons, LBs were used in combination with SOC instead of replacing it. Importantly, few studies have pointed toward LBs' cost-effectiveness for monitoring treatment response. Most health and budget impact analyses, especially those focused on lung cancer, suggest potential cost savings or a minimal-to-moderate budget impact. Nevertheless, additional research is needed to ascertain their effectiveness across various stages of lung and colorectal cancer, as well as to address potential modeling challenges.SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42022307939.</p

Gonadotrophin-releasing hormone receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

GnRH1 and GnRH2 receptors (provisonal nomenclature [35], also called Type I and Type II GnRH receptor, respectively [78]) have been cloned from numerous species, most of which express two or three types of GnRH receptor [78, 77, 107]. GnRH I (p-Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2) is a hypothalamic decapeptide also known as luteinizing hormone-releasing hormone, gonadoliberin, luliberin, gonadorelin or simply as GnRH. It is a member of a family of similar peptides found in many species [78, 77, 107] including GnRH II (pGlu-His-Trp-Ser-His-Gly-Trp-Tyr-Pro-Gly-NH2 (which is also known as chicken GnRH-II). Receptors for three forms of GnRH exist in some species but only GnRH I and GnRH II and their cognate receptors have been found in mammals [78, 77, 107]. GnRH1 receptors are expressed by pituitary gonadotrophs, where they mediate the effects of GnRH on gonadotropin hormone synthesis and secretion that underpin central control of mammalian reproduction. GnRH analogues are used in assisted reproduction and to treat steroid hormone-dependent conditions [53]. Notably, agonists cause desensitization of GnRH-stimulated gonadotropin secretion and the consequent reduction in circulating sex steroids is exploited to treat hormone-dependent cancers of the breast, ovary and prostate [53]. GnRH1 receptors are selectively activated by GnRH I and all lack the COOH-terminal tails found in other GPCRs. GnRH2 receptors do have COOH-terminal tails and (where tested) are selective for GnRH II over GnRH I. GnRH2 receptors are expressed by some primates but not by humans [81]. Phylogenetic classifications divide GnRH receptors into three [78] or five groups [122] and highlight examples of gene loss through evolution, with humans retaining only one ancient gene