Página 11 dos resultados de 1526 itens digitais encontrados em 0.002 segundos

The x-ray light valve: A low-cost, digital radiographic imaging system—Spatial resolution

MacDougall, Robert D.; Koprinarov, Ivaylo; Rowlands, J. A.
Fonte: American Association of Physicists in Medicine Publicador: American Association of Physicists in Medicine
Tipo: Artigo de Revista Científica
Português
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An x-ray light valve (XLV) coupled with an optical scanner has the potential to meet the need for a low-cost, high quality digital imaging system for general radiography. The XLV∕scanner concept combines three well-established, and hence, low-cost technologies: An amorphous selenium (a-Se) layer as an x-ray-to-charge transducer, a liquid crystal (LC) cell as an analog display, and an optical scanner for image digitization. The XLV consists of an a-Se layer and LC cell in a sandwich structure which produces an optical image in the LC layer upon x-ray exposure. The XLV∕scanner system consists of an XLV in combination with an optical scanner for image readout. Here, the effect of each component on the spatial resolution of an XLV∕scanner system is investigated. A theoretical model of spatial resolution of an XLV is presented based on calculations of the modulation transfer function (MTF) for a-Se and a LC cell. From these component MTFs, the theoretical MTF of the XLV is derived. The model was validated by experiments on a prototype XLV∕scanner system. The MTF of the scanner alone was obtained by scanning an optical test target and the MTF of the XLV∕scanner system was measured using x rays. From the measured MTF of the scanner...

Accelerating Medical Research using the Swift Workflow System

STEF-PRAUN, Tiberiu; CLIFFORD, Benjamin; FOSTER, Ian; HASSON, Uri; HATEGAN, Mihael; SMALL, Steven L.; WILDE, Michael; ZHAO, Yong
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2007 Português
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Both medical research and clinical practice are starting to involve large quantities of data and to require large-scale computation, as a result of the digitization of many areas of medicine. For example, in brain research – the domain that we consider here – a single research study may require the repeated processing, using computationally demanding and complex applications, of thousands of files corresponding to hundreds of functional MRI studies. Execution efficiency demands the use of parallel or distributed computing, but few medical researchers have the time or expertise to write the necessary parallel programs.

Single-detector polarization-sensitive optical frequency domain imaging using high-speed intra A-line polarization modulation

Oh, W. Y.; Vakoc, B. J.; Yun, S. H.; Tearney, G. J.; Bouma, B. E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/06/2008 Português
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We demonstrate a novel high-speed polarization-sensitive optical frequency domain imaging system employing high-speed polarization modulation. Rapid and continuous polarization modulation of light prior to illumination of the sample is accomplished by shifting the frequency of one polarization eigenstate by an amount equal to one quarter of the digitization sampling frequency. This approach enables polarization-sensitive imaging with a single detection channel and overcomes artifacts that may arise from temporal variations of the birefringence in fiber-optic imaging probes and spatial variation of birefringence in the sample.

Micropower CMOS Integrated Low-Noise Amplification, Filtering, and Digitization of Multimodal Neuropotentials

Mollazadeh, Mohsen; Murari, Kartikeya; Cauwenberghs, Gert; Thakor, Nitish
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2009 Português
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Electrical activity in the brain spans a wide range of spatial and temporal scales, requiring simultaneous recording of multiple modalities of neurophysiological signals in order to capture various aspects of brain state dynamics. Here, we present a 16-channel neural interface integrated circuit fabricated in a 0.5 μm 3M2P CMOS process for selective digital acquisition of biopotentials across the spectrum of neural signal modalities in the brain, ranging from single spike action potentials to local field potentials (LFP), electrocorticograms (ECoG), and electroencephalograms (EEG). Each channel is composed of a tunable bandwidth, fixed gain front-end amplifier and a programmable gain/resolution continuous-time incremental ΔΣ analog-to-digital converter (ADC). A two-stage topology for the front-end voltage amplifier with capacitive feedback offers independent tuning of the amplifier bandpass frequency corners, and attains a noise efficiency factor (NEF) of 2.9 at 8.2 kHz bandwidth for spike recording, and a NEF of 3.2 at 140 Hz bandwidth for EEG recording. The amplifier has a measured midband gain of 39.6 dB, frequency response from 0.2 Hz to 8.2 kHz, and an input-referred noise of 1.94 μVrms while drawing 12.2 μA of current from a 3.3 V supply. The lower and higher cutoff frequencies of the bandpass filter are adjustable from 0.2 to 94 Hz and 140 Hz to 8.2 kHz...

Information-theoretical analysis of time-correlated single-photon counting measurements of single molecules

Talaga, David S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 30/04/2009 Português
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Time correlated single photon counting allows luminescence lifetime information to be determined on a single molecule level. This paper develops a formalism to allow information theory analysis of the ability of luminescence lifetime measurements to resolve states in a single molecule. It analyzes the information content of the photon stream and the fraction of that information that is relevant to the state determination problem. Experimental losses of information due to instrument response, digitization, and different types of background are calculated and a procedure to determine the optimal value of experimental parameters is demonstrated. This paper shows how to use the information theoretical formalism to evaluate the number of photons required to distinguish dyes that differ only by lifetime. It extends this idea to include distinguishing molecular states that differ in the electron transfer quenching or resonant energy transfer and shows how the differences between the lifetime of signal and background can help distinguish the dye position in an excitation beam.

Potentials of Digitally Sampling Scintillation Pulses in Timing Determination in PET

Xie, Qingguo; Kao, Chien-Min; Wang, Xi; Guo, Ning; Zhu, Caigang; Frisch, Henry; Moses, William W.; Chen, Chin-Tu
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 06/10/2009 Português
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We investigate the potentials of digitally sampling scintillation pulses techniques for positron emission tomography (PET) in this paper, focusing on the determination of the event time. We have built, and continue building, a digital library of PET event waveforms generated with various combinations of photo-detectors and scintillator materials, with various crystal sizes. Events in this digital library are obtained at a high sampling of 20 GSps (Giga-samples per second) so that their waveforms are recorded with high accuracy. To explore the potential advantages of digitally sampling scintillation pulses, we employ a dataset in the above-mentioned library to evaluate two methods for digitizing the event pulses and linear interpolation techniques to analyze the resulting digital samples. Our results show that the two digitization methods that we studied can yield a coincidence timing resolution of about 300 ps FWHM when applied to events generated by a pair of LSO + PMT detector units. This timing resolution is comparable with that is achieved by the same detector pair with a constant fraction discriminator (CFD). As a benchmark, regular-time sampling (RTS) method, usually implemented with very fast traditional analog-to-digital converters (ADCs) for digitizing scintillation pulses...

A Pilot Study of Proteomic Profiles of Human Hepatocellular Carcinoma in the United States

Matos, Jesus M.; Witzmann, Frank A.; Cummings, O. William; Schmidt, C. Max
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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Human hepatocellular carcinoma (HCC) is one of the commonest causes of mortality among solid organ malignancies. The incidence of HCC in the United States is rising. Few proteomic biomarker studies have been done in U.S. populations. Tumor and nonmalignant tissue from three American patients with hepatitis and non-hepatitis-associated HCC were analyzed to find common differences in protein expression. Proteins were separated by 2D electrophoresis (isoelectric focusing followed by 10% SDS-PAGE). Gels were fixed and then stained with Coomassie brilliant blue. Digitization and processing were performed using the PDQuest software. The Student’s t-test was used to detect quantitative protein changes between tumor and nonmalignant liver consistent in all sample pairs with a cutoff made at P < 0.01. This yielded a total of 19 spots with significant (>2 fold) abundance changes. Matrix-assisted laser desorption ionization mass spectrometry analysis was performed using Waters Micomass M@LDI SYSTEM. The proteins were then identified using manual ProFound. Among the 19 spots, 9 showed overexpression and 10 showed underexpression in tumor. Overexpressed proteins included beta-5-tubulin, beta-actin, vimentin, carbamoyl-phosphate synthetase-1, methylenetetrahydrofolate dehydrogenase...

Artifacts in Fourier transform mass spectrometry

Mathur, Raman; O’Connor, Peter B.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/2009 Português
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Recent work on a new, higher sensitivity preamplifier design for Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) revealed a number of artifact peaks (spectral features) which do not contain useful chemical information. In order to determine the cause of these artifacts and eliminate them, these severely distorted spectra were compared with similarly distorted signal models. The source of several common signal processing artifacts was thereby determined and correlated to radio-frequency interference (RFI) noise and saturation of the amplifier and/or the digitizer. Under such conditions, the fast Fourier transform (FFT) generates spectral artifact peaks corresponding to harmonics and mixing frequencies of the real signal peaks and RFI frequencies. While this study was done using FTICRMS data, it is important to stress that these artifacts are inherent to the digitization and FFT process and thus are relevant to any FT-based MS instrument, including the orbitrap and FT ion trap.

Morphological Analysis of the Transverse Carpal Ligament

Pacek, Corey A.; Chakan, Matthew; Goitz, Robert J.; Kaufmann, Robert A.; Li, Zong-Ming
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Português
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Transection of the transverse carpal ligament (TCL) for carpal tunnel syndrome is commonly performed, yet actual knowledge of TCL morphology is rudimentary and the anatomical terminology is inconsistently used. The purpose of this study was to perform a morphological analysis of the TCL, to redefine the anatomical terminology concerning the TCL and surrounding structures, and to evaluate any correlation between external, measurable hand dimensions, and TCL dimensions. A silicone casting technique and digitization were employed to measure the morphology of the TCL in cadaveric specimens and to construct a three-dimensional TCL model. The TCL was the thickest distally at the midline and ulnar segments and the thickest proximally at the radial segment. External hand dimensions did not significantly correlate with TCL dimensions. The TCL thickness distribution is variable along the radioulnar axis. The thickness of the TCL was 2.1 ± 0.8 mm, ranging from 1.3 to 3.0 mm.

Cutting Edge: T cell receptor ligation triggers digital activation of NF-κB1

Kingeter, Lara M.; Paul, Suman; Maynard, Sean K.; Cartwright, Natalia G.; Schaefer, Brian C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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T cell receptor (TCR) mediated activation of the transcription factor NF-κB is required for T cell proliferation, survival, and effector differentiation. Although this pathway is the subject of intense study, it is not known whether TCR signaling to NF-κB is digital (switch-like) or analog in nature. Through analysis of the phosphorylation and degradation of IκBα and the nuclear translocation and phosphorylation of the NF-κB subunit RelA, we show that TCR directed NF-κB activation is digital. Furthermore, digitization occurs well upstream of the IKK complex, as PKCθ translocation to the immunologic synapse and activation-associated aggregation of Bcl10 and Malt1 also demonstrate both digital behavior and high correlation with RelA nuclear translocation. Thus, similar to the TCR-to-MAPK signaling cascade, analog antigen inputs are converted to digital activation outputs to NF-κB at an early step downstream of TCR ligation.

Prototype Medical Image Management System (MIMS) at the University of Pennsylvania: Software Design Considerations

Seshadri, Sridhar B.; Arenson, Ronald; Khalsa, Satjeet; Brikman, Inna; van der Voorde, Frans
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Português
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A 10 Mbits/second fiber-optic network for the transmission of chest x-ray images has been designed and implemented at our Hospital. Images are acquired with a high-resolution laser scanner. The viewing consoles display images at spatial resolutions of either 512 square or 1024 square. User interfaces have been designed to simplify the digitization and display processes. The applications level networking software and all the image processing software has been developed in-house. The system is now serving a 11-bed critical care facility on a day-to-day basis. This paper will focus on the software design issues. The software will be presented from a systems perspective. The importance of the user in the design process will be stressed and exemplified. The role of intelligent, rule-based software will be demonstrated. Selected clinical results will be discussed.

Review of the current state of whole slide imaging in pathology

Pantanowitz, Liron; Valenstein, Paul N.; Evans, Andrew J.; Kaplan, Keith J.; Pfeifer, John D.; Wilbur, David C.; Collins, Laura C.; Colgan, Terence J.
Fonte: Medknow Publications Pvt Ltd Publicador: Medknow Publications Pvt Ltd
Tipo: Artigo de Revista Científica
Publicado em 13/08/2011 Português
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Whole slide imaging (WSI), or “virtual” microscopy, involves the scanning (digitization) of glass slides to produce “digital slides”. WSI has been advocated for diagnostic, educational and research purposes. When used for remote frozen section diagnosis, WSI requires a thorough implementation period coupled with trained support personnel. Adoption of WSI for rendering pathologic diagnoses on a routine basis has been shown to be successful in only a few “niche” applications. Wider adoption will most likely require full integration with the laboratory information system, continuous automated scanning, high-bandwidth connectivity, massive storage capacity, and more intuitive user interfaces. Nevertheless, WSI has been reported to enhance specific pathology practices, such as scanning slides received in consultation or of legal cases, of slides to be used for patient care conferences, for quality assurance purposes, to retain records of slides to be sent out or destroyed by ancillary testing, and for performing digital image analysis. In addition to technical issues, regulatory and validation requirements related to WSI have yet to be adequately addressed. Although limited validation studies have been published using WSI there are currently no standard guidelines for validating WSI for diagnostic use in the clinical laboratory. This review addresses the current status of WSI in pathology related to regulation and validation...

A Reconfigurable Real-Time Compressive-Sampling Camera for Biological Applications

Fu, Bo; Pitter, Mark C.; Russell, Noah A.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 18/10/2011 Português
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Many applications in biology, such as long-term functional imaging of neural and cardiac systems, require continuous high-speed imaging. This is typically not possible, however, using commercially available systems. The frame rate and the recording time of high-speed cameras are limited by the digitization rate and the capacity of on-camera memory. Further restrictions are often imposed by the limited bandwidth of the data link to the host computer. Even if the system bandwidth is not a limiting factor, continuous high-speed acquisition results in very large volumes of data that are difficult to handle, particularly when real-time analysis is required. In response to this issue many cameras allow a predetermined, rectangular region of interest (ROI) to be sampled, however this approach lacks flexibility and is blind to the image region outside of the ROI. We have addressed this problem by building a camera system using a randomly-addressable CMOS sensor. The camera has a low bandwidth, but is able to capture continuous high-speed images of an arbitrarily defined ROI, using most of the available bandwidth, while simultaneously acquiring low-speed, full frame images using the remaining bandwidth. In addition, the camera is able to use the full-frame information to recalculate the positions of targets and update the high-speed ROIs without interrupting acquisition. In this way the camera is capable of imaging moving targets at high-speed while simultaneously imaging the whole frame at a lower speed. We have used this camera system to monitor the heartbeat and blood cell flow of a water flea (Daphnia) at frame rates in excess of 1500 fps.

The Digital Fish Library: Using MRI to Digitize, Database, and Document the Morphological Diversity of Fish

Berquist, Rachel M.; Gledhill, Kristen M.; Peterson, Matthew W.; Doan, Allyson H.; Baxter, Gregory T.; Yopak, Kara E.; Kang, Ning; Walker, H. J.; Hastings, Philip A.; Frank, Lawrence R.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 06/04/2012 Português
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Museum fish collections possess a wealth of anatomical and morphological data that are essential for documenting and understanding biodiversity. Obtaining access to specimens for research, however, is not always practical and frequently conflicts with the need to maintain the physical integrity of specimens and the collection as a whole. Non-invasive three-dimensional (3D) digital imaging therefore serves a critical role in facilitating the digitization of these specimens for anatomical and morphological analysis as well as facilitating an efficient method for online storage and sharing of this imaging data. Here we describe the development of the Digital Fish Library (DFL, http://www.digitalfishlibrary.org), an online digital archive of high-resolution, high-contrast, magnetic resonance imaging (MRI) scans of the soft tissue anatomy of an array of fishes preserved in the Marine Vertebrate Collection of Scripps Institution of Oceanography. We have imaged and uploaded MRI data for over 300 marine and freshwater species, developed a data archival and retrieval system with a web-based image analysis and visualization tool, and integrated these into the public DFL website to disseminate data and associated metadata freely over the web. We show that MRI is a rapid and powerful method for accurately depicting the in-situ soft-tissue anatomy of preserved fishes in sufficient detail for large-scale comparative digital morphology. However these 3D volumetric data require a sophisticated computational and archival infrastructure in order to be broadly accessible to researchers and educators.

TINA manual landmarking tool: software for the precise digitization of 3D landmarks

Schunke, Anja C; Bromiley, Paul A; Tautz, Diethard; Thacker, Neil A
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 05/04/2012 Português
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Generic real-time uniform K-space sampling method for high-speed swept-Source optical coherence tomography

Xi, Jiefeng; Huo, Li; Li, Jiasong; Li, Xingde
Fonte: Optical Society of America Publicador: Optical Society of America
Tipo: Artigo de Revista Científica
Publicado em 21/04/2010 Português
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We developed a universal, real-time uniform K-space sampling (Rt-UKSS) method for high-speed swept-source optical coherence tomography (SS-OCT). An external clock uniform in K-space was generated. The clock was synchronized with the zero-crossing time of an interferometric calibration signal and used as triggers for a high-speed data acquisition system in a point-by-point fashion, hence enabling uniform data sampling in K-space. Different from the numerical calibration algorithm commonly used in an SS-OCT system, the method reported here does not require over-sampling, thus greatly reducing the demand for digitization, data processing and storage speed. The Rt-UKSS method is adaptive and applicable to a generic SS-OCT system of a wide range of A-scan rates without special adjustment. We successfully implemented the Rt-UKSS method in an SS-OCT system based on a Fourier-domain mode-locked laser (FDML) of a 40-kHz scanning rate. Real-time imaging of biological tissues using such a system was demonstrated with a measured axial resolution of 9.3 μm and detection sensitivity greater than 120dB.

The US Virtual Herbarium: working with individual herbaria to build a national resource

Barkworth, Mary E.; Murrell, Zack E.
Fonte: Pensoft Publishers Publicador: Pensoft Publishers
Tipo: Artigo de Revista Científica
Publicado em 20/07/2012 Português
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The goal of the US Virtual Herbarium (USVH) project is to digitize (database, image, georeference) all specimens in all US herbaria, enabling them to be made available through a single portal. Herbaria house specimens of plants, fungi, and algae, so USVH will offer a rich portrait of biodiversity in the US and in the other countries represented in US herbaria. Equally importantly, working towards this goal will engage people with herbaria and the organisms they house, expanding their appreciation of both the power of biodiversity informatics and the demands that it places on data providers while developing improved communication among those working in and with herbaria. The project is not funded but has strong support among those working in herbaria. It works through regional herbarium networks, some of which existed prior to the USVH project, while others are still in gestation. It differs from most digitization projects in its emphasis on helping those involved with herbaria become part of a national enterprise, an aspect that is seen as critical to creating the resources needed to develop and sustain the project. In this paper, we present some of the lessons we have learned and the difficulties we have encountered during the first few years of the project.

Increasing the efficiency of digitization workflows for herbarium specimens

Tulig, Melissa; Tarnowsky, Nicole; Bevans, Michael; Anthony Kirchgessner, ; Thiers,  Barbara M.
Fonte: Pensoft Publishers Publicador: Pensoft Publishers
Tipo: Artigo de Revista Científica
Publicado em 20/07/2012 Português
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The New York Botanical Garden Herbarium has been databasing and imaging its estimated 7.3 million plant specimens for the past 17 years. Due to the size of the collection, we have been selectively digitizing fundable subsets of specimens, making successive passes through the herbarium with each new grant. With this strategy, the average rate for databasing complete records has been 10 specimens per hour. With 1.3 million specimens databased, this effort has taken about 130,000 hours of staff time. At this rate, to complete the herbarium and digitize the remaining 6 million specimens, another 600,000 hours would be needed. Given the current biodiversity and economic crises, there is neither the time nor money to complete the collection at this rate.

Nomenclatural benchmarking: the roles of digital typification and telemicroscopy

Wheeler, Quentin; Bourgoin, Thierry; Coddington, Jonathan; Gostony, Timothy; Hamilton, Andrew; Larimer, Roy; Polaszek, Andrew; Schauff, Michael; Solis, M. Alma
Fonte: Pensoft Publishers Publicador: Pensoft Publishers
Tipo: Artigo de Revista Científica
Publicado em 20/07/2012 Português
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Nomenclatural benchmarking is the periodic realignment of species names with species theories and is necessary for the accurate and uniform use of Linnaean binominals in the face of changing species limits. Gaining access to types, often for little more than a cursory examination by an expert, is a major bottleneck in the advance and availability of biodiversity informatics. For the nearly two million described species it has been estimated that five to six million name-bearing type specimens exist, including those for synonymized binominals. Recognizing that examination of types in person will remain necessary in special cases, we propose a four-part strategy for opening access to types that relies heavily on digitization and that would eliminate much of the bottleneck: (1) modify codes of nomenclature to create registries of nomenclatural acts, such as the proposed ZooBank, that include a requirement for digital representations (e-types) for all newly described species to avoid adding to backlog; (2) an “r” strategy that would engineer and deploy a network of automated instruments capable of rapidly creating 3-D images of type specimens not requiring participation of taxon experts; (3) a “K” strategy using remotely operable microscopes to engage taxon experts in targeting and annotating informative characters of types to supplement and extend information content of rapidly acquired e-types...

Image based Digitisation of Entomology Collections: Leveraging volunteers to increase digitization capacity

Flemons, Paul; Berents, Penny
Fonte: Pensoft Publishers Publicador: Pensoft Publishers
Tipo: Artigo de Revista Científica
Publicado em 20/07/2012 Português
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In 2010, the Australian Museum commenced a project to explore and develop ways for engaging volunteers to increase the rate of digitising natural history collections. The focus was on methods for image-based digitising of dry pinned entomology collections. With support from the Atlas of Living Australia, the Australian Museum developed a team of volunteers, training materials and processes and procedures.