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Effect of calcium hydroxide on the fracture resistance of dentin
No full textAn increased incidence of fracture has been reported in teeth where root canals were treated with calcium hydroxide. Edge chipping is one test used to measure the resistance of brittle materials to fracture. Presently, no studies have reported on edge chipping in teeth. This study evaluated the fracture resistance of human dentin exposed to calcium hydroxide for up to 60 days using the edge chipping method. Twelve recently extracted teeth were divided into a control group and three experimental groups with varying calcium hydroxide exposures. All teeth underwent pulpectomy via standard protocol. It was expected that the edge chip resistance would decrease as a function of exposure, but the results showed the converse. Chip resistance may reflect both the fracture resistance and the hardness of dentin, a quasi brittle material
The current SI seen from the perspective of the proposed new SI
No full textA revised International System of Units (SI) proposed by the International Committee for Weights and Measures is under consideration by the General Conference on Weights and Measures for eventual adoption. Widely recognized as a significant advance for both metrology and science, it is defined via statements that explicitly fix the numerical values of a selected set of seven reference constants when the values of these constants are expressed in certain specified units. At first sight this approach to defining a system of units appears to be quite different from that used to define the current SI. However, by showing how the definitions of the seven base units of the current SI also fix the numerical values of a set of seven reference constants (broadly interpreted) when the values of these constants are expressed in their coherent SI units, and how the definition of the current SI can be recast into the same form as that of the revised SI under consideration, we show that the revision is not as radical a departure from the current SI as it might initially seem
Findings and recommendations from the joint NIST-AGA workshop on odor masking
No full textSince the days of the alchemist, the observation that some substances have a smell while other substances do not has been a source of fascination. The sense of smell, or olfaction, is our least understood sense, however it is important for many human functions, including digestion, food selection and hazard avoidance. The detailed explanation of why individual chemicals (called odorants) might have a particular smell is still elusive. The situation with mixtures of odorants is even more complex and interesting. A number of distinct odorant mixture phenomena have been documented. Odorant suppression (sometimes called masking), conjugation (as described first by Zwaadermaker) and cross-adaptation are among a collection of such phenomena. They are related to the differential effects that one odorant species will have when mixed with another. Masking is a term that describes situations in which one odorant can overpower the sensation of another. There may be profound technological implications in a number of industrial sectors, most prominently in the fuel gas sector. Here, masking is suspected when the odorant that is added to natural gas can be detected by analytical instrumentation, but cannot be properly detected by an observer with a normal sense of smell. Note that this phenomenon is distinct from odor fade, which more properly describes a decrease in the concentration of an odorant rather than a decrease, disappearance or qualitative change in the perception of the odor in the absence of a change in absolute concentration. Anecdotal descriptions of masking events in the natural gas industry have persisted for over a decade, with the frequency of such events on the rise. Pursuant to the philosophy that the technological problem cannot be addressed until the basic science is understood, NIST, in collaboration with the American Gas Association (AGA), sponsored a workshop that brought together olfactory scientists and natural gas operations personnel in an effort to achieve a common understanding and identify critical research questions. This document is a summary of that workshop, and most importantly, a compendium of the findings and recommendations that resulted from the meeting
Selecting Valid Correlation Areas for Automated Bullet Identification System Based on Striation Detection
No full textSome automated bullet identification systems calculate a correlation score between two land impressions to measure their similarity. When extracting a compressed profile from the land impression of a fired bullet, inclusion of areas that do not contain valid individual striation information may lead to sub-optimal extraction and therefore may deteriorate the correlation result. In this paper, an edge detection algorithm and selection process are used together to locate the edge points of all tool-mark features and filter out those not corresponding to striation marks. Edge points of the resulting striation marks are reserved and expanded to generate a mask image. By imposing the mask image on the topography image, the weakly striated area(s) are removed from the expressed profile extraction. Using this method, 48 bullets fired from 12 gun barrels of six manufacturers resulted in a higher matching rate than previous studies
A Comparison of Methods for Computing the Residual Resistivity Ratio of High-Purity Niobium
No full textWe compare methods for estimating the residual resistivity ratio (RRR) of high-purity niobium and investigate the effects of using different functional models. RRR is typically defined as the ratio of the electrical resistances measured at 273 K (the ice point) and 4.2 K (the boiling point of helium at standard atmospheric pressure). However, pure niobium is superconducting below about 9.3 K, so the low-temperature resistance is defined as the normal-state (i.e., non-superconducting state) resistance extrapolated to 4.2 K and zero magnetic field. Thus, the estimated value of RRR depends significantly on the model used for extrapolation. We examine three models for extrapolation based on temperature versus resistance, two models for extrapolation based on magnetic field versus resistance, and a new model based in the Kohler relationship that can be applied to combined temperature and field data. We also investigate the possibility of re-defining RRR so that the quantity is not dependent on extrapolation
Workshop on Bridging Satellite Climate Data Gaps
No full textDetecting the small signals of climate change for the most essential climate variables requires that satellite sensors make highly accurate and consistent measurements. Data gaps in the time series (such as gaps resulting from launch delay or failure) and inconsistencies in radiometric scales between satellites undermine the credibility of fundamental climate data records, and can lead to erroneous analysis in climate change detection. To address these issues, leading experts in Earth observations from National Aeronautics and Space Administration (NASA), National Oceanic and Atmospheric Adminstration (NOAA), United States Geological Survey (USGS), and academia assembled at the National Institute of Standards and Technology on December 10, 2009 for a workshop to prioritize strategies for bridging and mitigating data gaps in the climate record. This paper summarizes the priorities for ensuring data continuity of variables relevant to climate change in the areas of atmosphere, land, and ocean measurements and the recommendations made at the workshop for overcoming planned and unplanned gaps in the climate record
Vacuum technology considerations for mass metrology
No full textVacuum weighing of mass artifacts eliminates the necessity of air buoyancy correction and its contribution to the measurement uncertainty. Vacuum weighing is also an important process in the experiments currently underway for the redefinition of the SI mass unit, the kilogram. Creating the optimum vacuum environment for mass metrology requires careful design and selection of construction materials, plumbing components, pumping, and pressure gauging technologies. We review the vacuum technology1 required for mass metrology and suggest procedures and hardware for successful and reproducible operation
Improve the strength of PLA/HA composite through the use of surface initiated polymerization and phosphonic acid coupling agent
No full textBioresorbable composite made from degradable polymers, e.g., polylactide (PLA), and bioactive calcium phosphates, e.g., hydroxyapatite (HA), are clinically desirable for bone fixation, repair and tissue engineering because they do not need to be removed by surgery after the bone heals. However, preparation of PLA/HA composite from non-modified HA usually results in mechanical strength reductions due to a weak interface between PLA and HA. In this study, a calcium-phosphate/phosphonate hybrid shell was developed to introduce a greater amount of reactive hydroxyl groups onto the HA particles. Then, PLA was successfully grafted on HA by surface-initiated polymerization through the non-ionic surface hydroxyl groups. Thermogravimetric analysis indiated that the amount of grafted PLA on HA can be up to 7 %, which is about 50 % greater than that from the literature. PLA grafted HA shows significantly different pH dependent æ-potential and particle size profiles from those of uncoated HA. By combining the phosphonic acid coupling agent and surface initiated polymerization, PLA could directly link to HA through covalent bond so that the interfacial interaction in the PLA/HA composite can be significantly improved. The diametral tensile strength of PLA/HA composite prepared from PLA-grafted HA was found to be over twice that of the composite prepared from the non-modified HA. Moreover, the tensile strength of the improved composite was 23 % higher than that of PLA alone. By varying additional variables, this approach has the potential to produce bioresorbable composites with improved mechanical properties that are in the range of natural bones, and can have wide applications for bone fixation and repair in load-bearing areas
Michael Rogers Rubin
No full textMichael Rogers Rubin
Inducted: 2011
Citation:
For guiding NIST to make consistently correct decisions through logic and outstanding legal counsel that continually met the highest ethical standards and unfailingly advocated for the taxpayer, NIST, and the law.
Tenure: 1988-2009
Birth: 1950, Washington, DC
Education:
Georgetown University, BA (Political Science), 1972
Georgetown University Law Center (Juris Doctor), 1976
Positions held:
Deputy Chief Counsel for NBS, 1988
Deputy Chief Counsel for Technology and NIST, 1990-2007
Chief Counsel for NIST, 2007-2009
Honors:
US Department of Commerce Silver Medal (1990) and Gold Medals (1995, 1996, and 2005)
US Department of Commerce, General Counsel’s Award, Attorney of the Year (2004)
Memberships:
The District of Columbia Bar
The Federal Bar Association
Impact and Publications:
For demonstrating exceptional leadership in advising NBS/NIST Mr. Rubin:
Assembled and lead a legal team that supported NIST in its technical investigation of the World Trade Center buildings collapse
Worked at the highest levels of the Department of Commerce to create regulations that guided NIST through a process resulting in creating the Advance Technology Program (ATP) and educated NIST’s technical and administrative staff on the importance and intricacies of those regulations.
Served in a leading role as NIST implemented the Fastener Quality Act (FQA) that protects national public health and safety by ensuring that fasteners used in critical situations conform to specifications.
Guided significant and groundbreaking legal work involving intellectual property protections, when Congress transformed NBS into NIST that enabled NIST to collaborate more fully with the private sector via CRADAs, SBIR Awards, and Cooperative Agreements
Worked closely with computer cyber security and privacy professionals at NIST and other parts of the Federal government for most of his tenure at the agency, which helped NIST to avoid multiple major pitfalls by allowing NIST’s technical professionals to focus on standards aligned with its mission.
Mr. Rubin’s in-depth knowledge of administrative law made him a reliable, respected expert among colleagues and senior officials in the Departments of Commerce and Justice and other parts of the government.
Mr. Rubin published multiple publications, including several books including:
Rubin, M.R., Information Economics and Policy in the United States Littleton, Colorado, Libraries Unlimited (1983)
Rubin, M.R., Public Rights, Private Wrongs: The Computer and Personal Privacy, John Wiley and Sons, New York, NY (1989
Sheldon Wiederhorn
No full textSheldon Wiederhorn
Inducted: 2011
Citation:
For pioneering the discipline of fracture mechanics in glass and ceramics, and leading a world-class team of NBS/NIST staff to develop the science of fracture mechanics of ceramics.
Tenure: 1963-2008
Birth: 1933, New York City, New York
Education:
Columbia University, BS (Chemical Engineering), 1956
University of Illinois, MS (Chemical Engineering), 1958
University of Illinois, PhD (Chemical Engineering), 1960
Positions held:
Research Chemist, Inorganic Materials Division, Institute for Materials Research, 1963-1968
Section Chief, Physical Properties Section, Inorganic Materials Division, IBS, 1968-1976
Chief, Fracture and Deformation Division, National Measurement Laboratory, 1976-1977
Deputy Division Chief, Fracture and Deformation Division, NML, 1977-1981
Group Leader, Mechanical Properties Group, Ceramics Division, NML, 1981-1988
Honors:
US Department of Commerce Silver Medal (1969), Gold Medal (1982)
Fellow, American Ceramic Society (1970)
Samuel Wesley Stratton Award (1977)
Member, National Academy of Engineering (1991)
American Ceramic Society Purdy Award (1969), Morey Award (1979), Sosman Lecture (1985), and Jeppson Award (1994)
Distinguished Lifetime Member of the American Ceramic Society (1998)
Member, World Academy of Ceramics (2010).
Memberships:
National Academy of Engineering
American Ceramic Society; ACS Basic Science Division, Chair (1974-1975), Board of Directors (2005-2008), Journal Editor (1989-1994)
Publications:
More than 200 publications including:
Wiederhorn, S.M., “Influence of Water Vapor on Crack Propagation in Soda-lime Glass,” J. Am Ceramic Soc. 50 [8], 407 (1967)
Wiederhorn, S.M. and Bolz, L.H, ""Stress Corrosion and the Static Fatigue of Glass"" J. Am. Ceram. Soc. 53[11], 543 (1970)
Evans, A.G. and Wiederhorn S.M., ""Proof Testing of Ceramic Materials - An Analytical Basis for Failure Prediction,"" Intl. J. of Frac. 10, 379 (1974)
Luecke, W.E., Wiederhorn, S.M., Hockey, B.J., Krause, R.F., Jr. and Long, G.G., ""Cavitation Contributes Substantially to Tensile Creep in Silicon Nitride,"" J. Am Ceram. Soc. 78 [8] 2085-96 (1995)
Guin, J.P. and Wiederhorn, S.M., “Fracture of Silicate Glasses: Ductile or Brittle?,” Phys. Rev. Let., 92 [21] 215502 (2004