Open Access to Archives

The OA Forum has commissioned this report from practising archivists in the UK and Sweden. It looks at the potential for using the Open Archives Initiative Protocol for Metadata Harvesting as a simple means of disseminating and exchanging archive catalogues. The world of conventional archives is interested in exchanging metadata, and has widely adopted international data structure standards produced by the International Council on Archives. It has also shown interest in a system for encoding catalogues known as Encoded Archival Description, or EAD. Archive descriptions are complex and collection based, proceeding from the general (fonds or collection level) to the particular (item level). The report briefly examines two implementations of OAI, the University of Illinois Project and the AIM25 project in the UK. It also considers a related hybrid implementation in Australia, and a planned use of the protocol in A2A, another UK project. It observes that OAI can be used for exchanging archive descriptions, but that there are problems. The first is difficulty in accurately reflecting linkages between levels of description. The second is the inconsistent application of EAD. The report also looks briefly at alternative means archivists are using for exchanging metadata, particularly the Z39.50 protocol. The report concludes that OAI will be used by conventional archives only if three conditions are fulfilled. First, archivists must be confident that compliant descriptions will respect archival principles, second, descriptions must be produced with little effort from existing systems, and third, archivists must believe that the wider OAI user base contains sufficient numbers of potential users. It suggests possible strategies in which archives would produce OAI compliant records for parts of their descriptions only

Automated Magnetic Field Scanning System

One of Jefferson Laboratory’s research areas is in Superconducting Radio Frequency (SRF) science and technology. SRF cavities are tested in the Vertical Testing Area (VTA) at Jefferson Laboratory, within a series of large cylindrical dewars. The measured quality factor (Q factor) of the SRF cavity is directly influenced by any existing magnetic field. Because the VTA previously housed a cyclotron, all the rebars within the building have residual magnetic fields emanating from them. This magnetic field effect of the building renders the measurements of Q factor on the devices inaccurate and the testing data unreliable. A magnetic field scanning system must be employed to accurately map the magnetic field within the testing dewar so that an existing set of current-carrying coils installed around the dewar can be used properly for cancellation of the residual magnetic fields. This process will ensure the initial testing conditions are free of any unwanted magnetic fields that could cause unreliable testing data. The proposed system will scan the residual magnetic field inside vertical dewars of varying sizes (16”- 34” diameter by 72”- 132” depth) in three dimensions and log data for later use, as well as display a visual mapping of the data to the operator through LabView. A sensor with a sensitivity of at least 0.1 milligauss will be attached to the bottom of a long pole that will be lowered into the dewar. Translation in the z direction, on the dewar’s central axis, will be achieved by using a pair of stepper motors controlling a rack and pinion set up on the center pole. To achieve incremental mapping in the x-y plane, an arm will be attached to the bottom of the pole that will house additional sensors. The platform holding the stepper motors will turn on a dial with degree measurements, allowing for rotational movement of the entire center pole and arm. By calculating the x-y values for each sensor on the arm at that set degree amount, mapping of set increments in the x-y plane can be achieved.https://scholarscompass.vcu.edu/capstone/1036/thumbnail.jp

The effect of off-axis seating on the marginal adaptation of full coverage all ceramic crowns

INTRODUCTION: No studies on the marginal gap or internal fit of crowns have reported the effect of non-axial seating which may often occur inadvertently clinically. AIM: Therefore this in vitro study sought to investigate the off-axis seating of CAD/CAM crowns and its effect on the marginal gap and internal fit. METHOD: A standardised crown preparation on a typodont tooth was used to design and mill 30 crowns with a flat occlusal surface. Ten Zirconia (Dentsply Sirona, Germany), 10 Enamic (Vita, Austria), and 10 Brilliant Crios (Coltene, Switzerland) crowns were milled, Ave of each milled with a luting space of 100µm, and Ave of 200µm. The marginal gap was measured in two and three dimensions after luting with silicone on a 3D-printed metal replica. Seating occurred axially, at 5° buccally and 5° lingually. The silicone was used to calculate the internal fit RESULTS: Axial seating with a 100 µm luting space obtained the smallest marginal gap, irrespective of material or luting space. 3D measurements were larger than 2D measurements, but not significantly. The maximum off-axis gap was 117µm, on the opposite side to which pressure was applied. CONCLUSIONS: Care must be taken clinically to ensure that luting takes place in an axial direction only