Silver Point Research Articles

Development of a New InGaAs Radiation Thermometer at NMIJ

The first InGaAs radiation thermometer at NMIJ was developed more than ten years ago as a standard radiation thermometer operating from 150 to 1,100°C. Its size-of-source effect (SSE) was as large as 1% from 6 mm in diameter to 50 mm in diameter. The new thermometer has an SSE of 0.3%. The reason for the error in measuring the SSE of InGaAs thermometers was also found. The new thermometer at first suffered from nonlinearity and the distance effect (DE). These deficiencies arose from the misalignment of optics inside the thermometer and were solved by increasing the detector size from 1 mm in diameter to 2 mm in diameter. Unfortunately, the detector of 2 mm diameter had a smaller S/N ratio than that of the 1 mm one at the indium (In) point. The final design uses a detector of 1 mm diameter, but the radiation is focussed on a smaller area of the detector. The new thermometer is smaller and lighter than preceding designs and other standard InGaAs radiation thermometers. The temperature of the main part of the instrument, including the filter, the detector, and the preamplifier board, is controlled at 30°C. In addition to the calibration with the six fixed points of copper (Cu), silver (Ag), aluminum (Al), zinc (Zn), tin (Sn), and indium (In), the linearity from the In point to the Cu point, the SSE, the DE, and the spectral responsivity were measured.

Uncertainties in the Realization of the SPRT Sub-ranges of the ITS-90

Working Group 3 of the Consultative Committee for Thermometry is responsible for recommending methods to assess uncertainties in contact thermometry. Accordingly, it has now completed a guide summarizing the uncertainties in the realization of the standard platinum resistance thermometer subranges of ITS-90 between the triple point of neon (24.5561K) and the freezing point of silver (961.78 °C). The document provides guidance to assess the uncertainties of both SPRT calibrations and temperature measurements. The document describes all known sources of uncertainty and influence variables, identifies key references in the literature that discuss, model or evaluate each effect, gives an indication of the typical magnitudes of the uncertainties, and provides propagation laws. This article is an overview of the guide emphasizing aspects that may be different from common practice, which includes: associating all uncertainty terms with a physical cause to ensure they can be propagated and to prevent double counting; uncertainty due to the oxidation state of the SPRT; uncertainty due to the isotopic composition of fixed-point substances; uncertainty due to impurities in fixed-point substances; and uncertainty due to non-uniqueness of the SPRT interpolations. The article gives a graphical summary of the total uncertainties in ITS-90 over the SPRT temperature range.

A Schottky-Diode Model of the Nonlinear Insulation Resistance in HTSPRTs—Part II: Detailed Two- and Three-Wire Measurements

Electrical leakage is a significant factor in the uncertainty of temperature measurements employing high-temperature standard platinum-resistance thermometers, with effects as large as several millikelvin at the freezing point of silver (962°C). The insulation resistance also exhibits complex behavior that includes non-linearities, sensitivity to the electrical environment, and the generation of spurious voltages and currents. In an earlier article, it was suggested that the behavior is consistent with the existence of metal–semiconductor diodes, also known as Schottky-barrier or point-contact diodes, formed at the points of contact between platinum wire and fused-silica insulators supporting the platinum. In this article, we describe detailed measurements of the non-linear resistance of a fused-silica insulator supported by platinum wires. The discussion includes a detailed description of the measurement system, and the results of two experiments that show many of the features suggested by the metal–semiconductor-diode model. Observed features in the current–voltage measurements include an S-shaped feature characteristic of back-to-back diodes, temperature dependence of saturation currents consistent with thermionic emission, and a diode polarity consistent with silica being a p-type semiconductor. Some impacts of the model on thermometry practice are also noted.

Propagation of Uncertainty Due to Non-linearity in Radiation Thermometers

The measurement of the non-linearity of radiation thermometers is important in the realization of ITS-90 above the silver point and in the calibration of primary or secondary radiation thermometers using multiple fixed points both above and below the silver point. A non-linearity function is usually derived, enabling correction of the measured signals. Uncertainties in this non-linearity function propagate to the uncertainty in the determination of an unknown temperature. Since the same non-linearity function is used both during calibration and in subsequent use of the thermometer, there is a high degree of correlation between the uncertainties in the corrected calibration signals and the corrected in-use signals. While these correlations obviously lead to zero uncertainty at the calibration points, it is difficult to determine the correlation coefficients for temperatures away from these points. This article sets out a mathematical framework, based on interpolation theory, for propagating the uncertainty due to non-linearity in which correlation is easily included. The method is illustrated for a thermometer realizing ITS-90 up to 3,000°C based on one fixed point (silver, gold, or copper), and also for alternative realization schemes based on two or more fixed points. The total non-linearity uncertainty for the multipoint schemes is considerably lower than for the ITS-90 method. The mathematical framework can also be applied to secondary calibrations below the silver point, where non-linearity is typically more problematic for the detectors used in this temperature range.

Theoretical Calculation of the Low-Density Transport Properties of Monatomic Silver Vapor

Calculations of low-density transport property collision integrals are used to obtain the high-temperature transport properties of silver atoms as a function of temperature. The collision integrals depend on the two-body interaction potentials between silver atoms in various electronic states. Contributions are included from the ground $$X^{1}\Sigma_{\rm g}^{+}$$ and excited $$^{3}\Sigma _{\rm u}^{+}$$ molecular electronic states of the silver dimer that dissociate to two ground-state silver atoms and from the excited $$A^{1}\Sigma_{\rm u}^{+}$$ molecular state that dissociates to a ground state and an excited state silver atom. Spectroscopic constants are available for these three electronic states, and these spectroscopic constants have been used to determine the Hulburt–Hirschfelder (HH) potentials for these three states. The HH potential is perhaps the best general-purpose potential for representing atom–atom interactions. This potential depends only on the spectroscopic constants, and can be used to calculate the viscosity and diffusion collision integrals for the three molecular electronic states. The collision integrals are then degeneracy averaged over the three states. The heat capacity of silver atoms is also calculated at high temperatures. These results provide the information required to obtain the thermal conductivity, viscosity, and self-diffusion coefficients of silver atoms over a wide temperature range from the boiling point of silver to temperatures at which ionization becomes important.

Root canal preparation with the NiTi systems K3, Mtwo and ProTaper

The aim of this paper was to examine the result of rotary root canal preparation with the nickel-titanium (NiTi) systems K3, ProTaper and Mtwo. One hundred and fifty curved artificial root canals and 60 mesial canals of human mandibular molars were selected. In the group of curved artificial canals, all canals were prepared to size 35/0.04 taper with the three systems. In the group of human mandibular molars, the teeth with mature root canals were radiographed with silver points inserted in bucco-lingual and in mesio-distal positions. In the artificial root group, one K3 instrument separated. Mtwo (20%) showed significantly (P = 0.003) less zips than K3 (46.9%) or ProTaper (50%). There were no significant differences in ledge and elbow formation. K3 and Mtwo had the lowest percentage of canal transportation. There was no significant difference regarding the preparation length or the condition of the apical foramina following the preparation. Canals prepared with K3 (26.5%) were significantly (P < 0.001) less tapered than ProTaper (62%) and Mtwo (82%). In the human mandibular molar group, one Mtwo and one ProTaper instrument separated. No significant differences were found in the preparation length, transportation or taper. The three systems tested, K3, Mtwo and ProTaper, achieved good preparation results.

Uncommon radiological findings: a case report

A 50-year-old friendly and attractive Chinese lady was examined by the Primary Care Unit, Faculty of Dentistry, University of Malaya. Her requests for treatment included implants and crowns. Two periapical radiographs of teeth 16 and 48 were taken to aid diagnosis. Interestingly, pin-like radio-opaque objects were found over the crown of the impacted tooth 15 and also tooth 17. These objects were initially interpreted as silver points or radiographic artifacts but further investigation employing panoramic radiography revealed the distribution of more radio-opaque objects in the orofacial region. Based on a review of the literature and the opinion of experienced radiology and oral surgery lecturers, these foreign radio-opaque objects were diagnosed as susuks or charm needles.

V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;-Doped M&lt;sup&gt;2+&lt;/sup&gt;Cu&lt;sub&gt;2&lt;/sub&gt;Nb&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;8&lt;/sub&gt; Compounds (M&lt;sup&gt;2+&lt;/sup&gt;= Zn, Co, Ni, Mg &amp; Ca) for Microwave Dielectric LTCCs

The copper-niobates, M2+Cu¬2Nb2O8 (M2+ = Zn, Co, Ni, Mg or Ca) have good microwave dielectric properties when sintered between 985 – 1010oC, and 1110oC for CaCu¬2Nb2O8. Therefore they would be potential dielectric Low Temperature Co-fired Ceramic (LTCC) materials if they could be made to sinter below 960oC (melting point of silver). To this end, additions of 3wt% V2O5 were made to ZnCu2Nb2O8, CoCu2Nb2O8, NiCu2Nb2O8, MgCu2Nb2O8 and CaCu2Nb2O8, and their sintering and dielectric behaviour was investigated for samples fired between 800 and 950oC. Doping lowered sintering temperatures to below the 960oC limit in all cases. Doping had the general effect of reducing r, density, Qf and f, although doped CaCu2Nb2O8 had a Qf value of 9300 GHz, nearly four times that of the best undoped sample. When doped and undoped samples all fired to 935oC were compared, all doped samples had greater r and density, and all except ZnCu2Nb2O8 had a smaller f.

Bilateral comparison of the NRC and PTB local realizations of the ITS-90 between the silver point and 1700 °C using vacuum tungsten strip lamps as transfer standards

At its 19th session in September 1996, the Consultative Committee for Thermometry (CCT) agreed to conduct an international key comparison of the local realizations of the International Temperature Scale (ITS) of 1990 above the silver point. High-stability tungsten-strip lamps were selected as transfer standards. The measurements began in 1997 and ended in July 1999. The comparison was piloted by the NMi-VSL and co-piloted by the NPL. The national metrology institutes of 12 countries participated in this key comparison and the initial Draft A report was circulated in October 1999. With the circulation of the report, some participants became aware of problems with their local scale realizations. To link their improved local scale realization to the CCT-K5 results, the NRC asked the PTB to pilot a bilateral comparison of the realization of the ITS-90 between the silver point and 1700 °C using a pair of tungsten-strip lamps as transfer standards. The measurements were carried out from June 2001 to October 2002.The results of the bilateral comparison presented in figures 1 and 2 clearly demonstrate that the NRC and PTB local scale realizations of the ITS-90 between the silver point and 1700 °C agree within the combined standard uncertainty. As the scale realization of the PTB remained unchanged since the measurements performed for the CCT-K5, this bilateral comparison has successfully linked the improved scale realization of the NRC to the results of the key comparison via the stable scale realization of the PTB. Figure 1. Differences between the radiance temperatures of lamp C598 measured at the NRC and the PTB. (NRC_I, NRC_II, NRC_average: temperature measured at the NRC for the first and second run, and average temperature measured at the NRC, respectively. Dotted line: combined standard uncertainty at k = 1.) Figure 2. Differences between the radiance temperatures of lamp 644C measured at the NRC and the PTB. (NRC_I, NRC_II, NRC_average: temperature measured at the NRC for the first and second run, and average temperature measured at the NRC, respectively. Dotted line: combined standard uncertainty at k = 1.)Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Novel microwave dielectric LTCCs based uponV 2O 5 doped M 2+Cu 2Nb 2O 8 compounds (M 2+ = Zn, Co, Ni, Mg and Ca)

The copper-niobates, M 2+Cu 2Nb 2O 8 (M 2+ = Zn, Co, Ni, Mg or Ca) have good microwave dielectric properties when sintered between 985–1010 °C and 1110 °C for CaCu 2Nb 2O 8. Therefore, they would be potential dielectric LTCC materials if they could be made to sinter below 960 °C (melting point of silver). To this end, additions of 3 wt.% V 2O 5 were made to ZnCu 2Nb 2O 8, CoCu 2Nb 2O 8, NiCu 2Nb 2O 8, MgCu 2Nb 2O 8 and CaCu 2Nb 2O 8, and their sintering and dielectric behaviour was investigated for samples fired between 800 and 950 °C. Doping lowered sintering temperatures to below the 960 °C limit in all cases. Doping had the general effect of reducing ɛ r, density, Qf and τ f, although doped CaCu 2Nb 2O 8 had a Qf value of 9300 GHz, nearly four times that of the best undoped sample. Doped ZnCu 2Nb 2O 8 fired to 935 °C had Qf = 10,200 GHz, and for doped CoCu 2Nb 2O 8 fired to 885 °C Qf = 7500 GHz. When doped and undoped samples all fired to 935 °C were compared, all doped samples had greater ɛ r and density, and all except ZnCu 2Nb 2O 8 had a smaller τ f. All doped samples had a more linear relationship between frequency and temperature in the range 250–300 K.

Silver Nanoparticles from Ultrasonic Spray Pyrolysis of Aqueous Silver Nitrate

Silver particles less than 20 nm in diameter were synthesized by pyrolysis of an ultrasonically atomized spray of highly dilute aqueous silver nitrate solution at temperatures above 650°C and below the melting point of silver. Feed solution concentration and ultrasound power applied to the atomizer were found to have a significant impact on the particle size of the silver nanoparticles. Average particle size was found to be controllable in the range of 20 nm to 300 nm by varying the solution concentration and the ultrasound power to the atomizer.

Low temperature sintering of iron deficient Z type hexagonal ferrites

Low temperature sintering of iron deficient hexagonal Co 2Z type ferrites is attempted to prepare a chip inductor for ultra high frequency uses. It should be attained below the melting point of silver (960 °C) used as the electrode material of the chip inductor. The best result is obtained for the sample with the composition 2.15Co 0.6Cu 0.4O·3Ba 0.79Sr 0.16Bi 0.05O·9.725Fe 2O 3 sintered at 925 °C containing 0.5 wt.% of lithium bismuth oxide as a sintering additive. Its density and permeability reaches 5.0 g/cm 3 and 7, respectively. As a result, the impedance of the chip inductor also reaches 390 ohm at 2 GHz using this material.

NUCLEAR PHYSICS and PAINTING: Sub-topic of the wide and fascinating field of SCIENCE and ART

The goal of this article is to briefly present a few examples where nuclear methods ⁎ and instruments have been proven useful in analyzing paintings. In particular it will be illustrated how to: a) Discover a self portrait of Van Dyck with NEUTRONS. b) Unmask a forgery with PROTONS. c) Explore the mystery of silver point drawings with PROTONS.

A method for indirect measurements of the parameters of platinum resistance thermometers at the freezing point of silver

A method for indirect measurements of the parameters of platinum resistance thermometers at the freezing point of silver

A method for indirect measurements of the parameters of platinum resistance thermometers at the freezing point of Silver

A procedure for reproducing the International Temperature Scale ITS-90 for solving special measurement problems is considered.

A comparison of PRTs at the Cu–Ag eutectic point (780 °C)

Twelve platinum resistance thermometers (PRTs) were repeatedly calibrated between the triple point of water and the silver point. During each calibration their resistance was also determined at the Cu–Ag eutectic point. The temperatures indicated by the PRTs were within ±1 mK, except for one that differed by 4 mK from the average, 779.6360 °C, of the other eleven.Four of these PRTs had a lower W (Ag) value than acceptable by the ITS-90, including the one that differed by 4 mK. Thus, within this set of PRTs all the ‘acceptable’ ones and three out of four ‘unacceptable’ ones indicated a unique temperature within 1 mK halfway between the aluminium and the silver points.

Did squinting cause the 'Dürerblick'?

During his working life, Albrecht Dürer (1471–1528) produced a number of oil paintings, over 400 prints and about 1200 drawings (Strieder 1982). His highly detailed and inspired woodcuts and copperplate engravings were brilliant. Some of Dürer's allegorical work, such as ‘Melencolia’ (Fig. 1), tempts its observers to make their own interpretations, but it has always refused to give up all its secrets. Melencolia 1. Albrecht Dürer. Copperplate engraving, 1514. 24 × 19 cm. An explanatory text on the painting ‘Piper and Drummer’ (Fig. 2) (Polland 1991) states that the drummer is gazing toward the piper with empathy, and claims that the drummer is a hidden self-portrait of Dürer. This appears to be highly likely, as the figure bears a striking resemblance to those in other self-portraits. However, when we look more closely at this painting (Fig. 3), we see that Dürer's right eye squints outwards and upwards, while his left eye stares straight ahead. Dürer suffered from a right-side exotropia and hypertropia. In the German literature on the subject, this look is referred to as the ‘Dürerblick’ (Strebel 1937) and it is seen repeatedly in his many self-portraits (Fig. 4). The fact that this is actually a case of a defective position of the left eye − because Dürer used a mirror to paint his self-portraits − is irrelevant in this connection. Piper and Drummer. Albrecht Dürer. Oil on wood, 1503–1504. 95 × 51 cm. Reproduced with permission of the Wallraf-Richartz Museum, Cologne. Detail of Fig. 2. Self-portrait with Landscape. Albrecht Dürer. Oil on wood, 1498. 52 × 41 cm. Reproduced with permission of the Prado Museum, Madrid. A defective eye position is also seen in ‘Self-portrait with Bandage’ (Fig. 5), and, looking at this drawing, we may wonder why Dürer was holding his hand in front of his right eye. Could he have suffered from a paralysis with diplopia? If this were so, it would explain his compensatory turning of the head in the self-portraits and account for the fact that he holds his hand in front of his right eye. In any event, Dürer showed no sign of squinting at 13 years of age (Fig. 6), although the same defective position of the eye can be detected in a portrait of his mother (Fig. 7), which would imply that he might have inherited a tendency to squint. In contrast, no such defective position is seen in the well-known portrait of Dürer's father that hangs in the National Gallery in London. Self-portrait with Bandage. Albrecht Dürer. Pen drawing, 1491. 20 × 21 cm. Repro-duced with permission of the University Library of Erlangen-Nürnberg. Self-portrait as a Boy. Albrecht Dürer. Silver point drawing, 1484. 27 × 20 cm. Re-produced with permission of the Albertina Museum, Vienna. Dürer's Mother Barbara. Albrecht Dürer. Charcoal drawing, 1514. 41 × 30 cm. Re-produced with permission of the City Museum of Berlin. Dürer was a painter who idealized his subjects to a great extent; he was also marked by the religion of his time. He was a major theoretician and wrote many treatises on subjects such as perspective. He may have suffered from incomplete binocular vision due to his squinting. He may also have been nearsighted in his squinting eye, which in many self-portraits appears to be larger than the other eye. In certain paintings, such as ‘Birth of Christ’ (Alte Pinakothek, Munich), the picture appears to be compressed, which could indicate some difficulty with binocular vision. It is also interesting that many of his paintings include extremely small, detailed figures. It would be difficult for a painter with normal vision to execute these miniatures, as well as his detailed copper plate engravings, without using a magnifying glass, which in all probability Dürer did not have. Possible nearsightedness in one eye would undeniably have made such painting easier.

Competition Necessarily Tends to Produce Excess: The Experience of Free Banking in Switzerland

Abstract According to McCulloch, Longfield and Loyd, a free banking system is always prone to overissues of bank notes. Their view is supported by the free banking era in Switzerland (1826-1907), where, due to competitive pressures within the banking community and the absence of note-brand loyalty on the part of the general public, overissues (causing a rise in the foreign exchange rates above the upper gold and silver points) finally became permanent. Free competition, therefore, had to give way to collusive action and, in 1907 (with the open consent of the issuing banks), to the establishment of the Swiss National Bank.

Endodontic treatment performed by Flemish dentists. Part 2. Canal filling and decision making for referrals and treatment of apical periodontitis.

To gather information on root-canal treatment carried out by dentists working in Flanders (Belgium). A questionnaire reported in a previous study was also used to gather information on canal medicaments, canal filling, and in decision making for referrals and treatment of apical periodontitis. Calcium hydroxide as an interappointment dressing was used by 69.7% of the respondents. Approximately one-third of the respondents did not use any intracanal medicament. Caustic products used for pulp tissue fixation were used by 66.8% of the respondents. Cavit (48.2%) and glass-ionomer (31.3%) were the temporary coronal-filling materials used most often, followed by zinc oxide-eugenol and IRM(R). Cold lateral condensation of gutta-percha was the filling technique most used by the respondents (65.8%). Single-cone gutta-percha placement (16%), paste techniques (4.9%) and silver points (3.9%) were still used. Resin-based sealers were used most often (88.6%). Paraformaldehyde containing sealers such as Endomethasone and N2 were used infrequently. Approximately half of the practitioners were satisfied with their canal-filling technique, others felt that they could do better (43.0%); 0.7% were not satisfied. In cases with apical periodontitis, the size of periapical lesions and/or the presence of a root filling influenced the choice of endodontic treatment. The most common reasons for referral of endodontic cases were: retrieval of silver points, surgery, and post removal. The results of this study indicate that techniques and methods used for canal medication and canal filling were acceptable for the majority of the respondents. Re-treatment was underestimated as a treatment option.

Propagation of uncertainty for non-linear calibration equations with an application in radiation thermometry

Analytic expressions are derived for the sensitivity coefficients for the uncertainties in both the x and y calibration points for an arbitrary non-linear calibration equation, y = y(x). Formalisms for the propagation of uncertainty are given for both exact fitting and least-squares determinations of the adjustable parameters. These formulae are applied to the approximation of ITS-90 above the silver point by radiation thermometry, using the recently developed metal–carbon and metal-carbide–carbon eutectic fixed points. A modified form of the non-linear Sakuma–Hattori calibration equation is analysed. It is shown that for temperatures between the fixed points, the combined uncertainty can be kept below the uncertainty in the individual calibration points, and reduces as the number of degrees of freedom for least-squares fitting increases.