Well-structured and publicly accessible databases represent core resources for modern data-rich research as they consolidate filed-specific knowledge and highlight both best practices and challenges ...faced by each discipline. Further impactful growth of nanomaterials databases requires concerted efforts between database stewards, researchers, funding agencies, and publishers.
Evaluating the implications of nanomaterials in biological and environmental systems can be difficult without sufficient characterization of the nanomaterials’ physico-chemical characteristics (PCC). ...Additionally, while nanomaterials possess inherent characteristics, their acquired characteristics can change based on the system under consideration or even the test method or protocol used for the characterization. The Nanomaterial Registry, an authoritative resource for nanomaterial data, has established minimal information about nanomaterials (MIAN) for PCC. The MIAN is used as a guideline for curating and archiving the nanomaterial information that is vital to understanding the biological and environmental implications of these materials. This manuscript details the MIAN developed and provides examples of curated data. The MIAN and Registry data model are flexible, and can accommodate new information and insights as scientific discovery regarding nanomaterials evolves. Through the use of the MIAN, the Registry archives sufficient metadata to allow the user to easily access the original/source study records of interest.
The amount of data being generated in the nanotechnology research space is significant, and the coordination, sharing, and downstream analysis of the data is complex and consistently deliberated. The ...complexities of the data are due in large part to the inherently complicated characteristics of nanomaterials. Also, testing protocols and assays used for nanomaterials are diverse and lacking standardization. The Nanomaterial Registry has been developed to address such challenges as the need for standard methods, data formatting, and controlled vocabularies for data sharing. The Registry is an authoritative, web-based tool whose purpose is to simplify the community's level of effort in assessing nanomaterial data from environmental and biological interaction studies. Because the Registry is meant to be an authoritative resource, all data-driven content is systematically archived and reviewed by subject-matter experts. To support and advance nanomaterial research, a set of minimal information about nanomaterials (MIAN) has been developed and is foundational to the Registry data model. The MIAN has been used to create evaluation and similarity criteria for nanomaterials that are curated into the Registry. The Registry is a publicly available resource that is being built through collaborations with many stakeholder groups in the nanotechnology community, including industry, regulatory, government, and academia. Features of the Registry website (http://www.nanomaterialregistry.org) currently include search, browse, side-by-side comparison of nanomaterials, compliance ratings based on the quality and quantity of data, and the ability to search for similar nanomaterials within the Registry. This paper is a modification and extension of a proceedings paper for the Institute of Electrical and Electronics Engineers.
Many groups within the broad field of nanoinformatics are already developing data repositories and analytical tools driven by their individual organizational goals. Integrating these data resources ...across disciplines and with non-nanotechnology resources can support multiple objectives by enabling the reuse of the same information. Integration can also serve as the impetus for novel scientific discoveries by providing the framework to support deeper data analyses. This article discusses current data integration practices in nanoinformatics and in comparable mature fields, and nanotechnology-specific challenges impacting data integration. Based on results from a nanoinformatics-community-wide survey, recommendations for achieving integration of existing operational nanotechnology resources are presented. Nanotechnology-specific data integration challenges, if effectively resolved, can foster the application and validation of nanotechnology within and across disciplines. This paper is one of a series of articles by the Nanomaterial Data Curation Initiative that address data issues such as data curation workflows, data completeness and quality, curator responsibilities, and metadata.
This paper demonstrates that chromaticity shifts in light-emitting diode (LED) devices arise from multiple mechanisms that produce chemical changes in the materials used to construct the LED devices. ...Each chromaticity change is shown to proceed over a finite period of time, and there is a limit on the impact of each shift. For example, chromaticity shifts in LED devices usually start with a fast-acting component that quickly reaches a maximum value, followed by one or more slower acting component(s). This behavior can be modeled analytically with a bounded exponential component to describe the fast-acting component, followed by one or more generalized logistic models. These analytical models contain several key parameters, including the limiting value of each chromaticity shift (A for the upper asymptote and L for the lower asymptote) and the rate of the change k.
This approach to chromaticity modeling is demonstrated with analytical models of the chromaticity shifts caused by the irreversible degradation of phosphors. These analytical models provide insights into the kinetic processes responsible for green and red chromaticity shifts caused by phosphor degradation. A green shift is produced by the surface oxidation of the nitride phosphor that changes the emission profile to lower wavelengths. As the surface oxidation reaction proceeds, surface reactants are consumed thereby slowing the reaction rate, and the bulk oxidation processes become more prevalent. A red chromaticity shift can arise from quenching of the green phosphor which shift the emission in the red direction. This paper concludes by discussing the implications of these models for projecting chromaticity for different operational conditions.
•Changes in phosphor performance in LED devices can produce chromaticity shifts. For example, oxidation of nitride phosphors changes the phosphor emission wavelengths and results in a chromaticity shift in the green direction. In contrast, quenching of green phosphors can produce a chromaticity shift in the red direction.•The chemical processes responsible for chromaticity shifts in LED devices have a beginning and an end. They do not proceed indefinitely.•In some cases, the end of a chromaticity shift can exceed an acceptable parametric limit (e.g., Δu′v′ ≥ 0.007), while in many cases the chemical pocesses causing the shift may only change chromaticity by a small amount (e.g., 1-step to 3-step MacAdam ellipses).•Chromaticity shifts can be modeled with a combination of a bounded exponential function and one or more logistic functions lower shifts).•Understanding and modeling chromaticity shifts is necessary before projections of long-term behavior can be made.
Liquid organic scintillators are cocktails of aromatic fluorophores in an aromatic solvent. They find widespread use in Liquid Scintillation Counters with applications in medical diagnostics as well ...as fundamental nuclear and particle physics. Ultima Gold™ XR, a commercially available organic liquid scintillator from Perkin Elmer, can be used in both aqueous and non-aqueous systems and is typically used for beta detection in medical diagnostics. Its performance under gamma radiation and neutron radiation is less well-characterized.
Special and normal Ultima Gold™ XR liquid scintillators were exposed in separate experiments to fast neutrons and high energy photons from a nuclear reactor and to gamma rays from a Co-60 source. To perform the measurements in the radiation chamber, a custom light collection system consisting of a fiber optic cable, spectrometer and a diffuse reflecting optical cavity was fabricated. Advanced calibration procedures, traceable to NIST standards, were developed to determine photon fluxes and flux densities of the scintillators under ionizing radiation conditions. The scintillator emission spectra under gamma radiation from a Co-60 source and neutron radiation from a pool-type nuclear reactor were recorded and compared. Results on the spectrometer design and comparison of the spectra under different exposure are presented.
This work is one of a series of articles by the Nanomaterial Data Curation Initiative. Other articles in this series discuss data curation workflows, data completeness and quality, curator ...responsibilities, and metadata. Many groups within the broad nanotechnology field are already developing data repositories and tools driven by their individual organizational goals. Integrating these data across disciplines, and with other non-nanotechnology resources, can support multiple objectives by reusing the same information, and can serve as the impetus for novel scientific discoveries through deeper data analyses. Based on the results of a community-based survey of organizations that maintain nanomaterial repositories, this article discusses current data integration practices in nanoinformatics and mature fields such as genomics, as well as nanotechnology-specific challenges impacting data integration. Recommendations for achieving integration of existing operational nanotechnology resources, as based on results from a community-wide survey, are presented herein. Nanotechnology-specific data integration challenges, if effectively resolved, can foster the application and validation of nanotechnology within and across disciplines.
Two-channel tunable white lighting (TWL) systems represent the next wave of solid-state lighting (SSL) systems and promise flexibility in light environment while maintaining the high reliability and ...luminous efficacy expected with SSL devices. TWL systems utilize LED assemblies consisting of two different LED spectra (i.e., often a warm white assembly and a cool white assembly) that are integrated into modules. While these systems provide the ability to adjust the lighting spectrum to match the physiology needs of the task at hand, they also are a potentially more complex lighting system from a performance and reliability perspective. We report an initial study on the reliability performance of such lighting systems including an examination of the lumen maintenance and chromaticity stability of warm white and cool white LED assemblies and the multi-channel driver that provides power to the assemblies. Accelerated stress tests including operational bake tests conducted at 75°C and 95°C were used to age the LED modules, while more aggressive temperature and humidity tests were used for the drivers in this study. Small differences in the performance between the two LED assemblies were found and can be attributed to the different phosphor chemistries. The lumen maintenances of both LED assemblies were excellent. The warm white LED assemblies were found to shift slightly in the green color direction over time while the cool white LED assemblies shifted slightly in the yellow color direction. The net result of these chromaticity shifts is a small, barely perceptible reduction in the tuning range after 6,000 hours of exposure to an accelerating elevated temperature of 75°C.
Meeting the longevity requirements of solid-state lighting (SSL) devices places extreme demands on the materials and designs that are used in SSL luminaires. Therefore, understanding the aging ...characteristics of lens, reflectors, and other materials is essential to projecting the long-term performance of LED-based lighting systems. Overlooking these factors at either the design or product specification stage can result in premature failure of the device due to poor luminous flux maintenance and/or excessive chromaticity shifts. This paper describes a methodology for performing accelerated stress testing (AST) on materials intended for use in SSL luminaires. This test methodology, which consists of elevated temperature and humidity conditions, produces accelerated aging data that can be correlated to expected performance under normal luminaire operating conditions. The correlations can then be leveraged to produce models of the changes in the optical properties of key materials including transmittance versus wavelength of lenses and reflectance versus wavelength for housings and other reflectors. This information has been collected into a lumen maintenance decision support tool (LM-DST) and together with user supplied inputs (e.g., expected operation conditions) can provide guidance on lifetime expectations of SSL luminaires. This approach has been applied to a variety of materials commonly found in SSL luminaires including acrylics, polycarbonates, and silicones used for lenses and paints, coatings, films, and composites used for reflectors.
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