Density Difference Measurements Research Articles

External Magnetic Field Measurements in UME Kibble Balance

The new definition of kilogram in terms of the fixed value of Planck constant ensures the long-term stability of SI mass unit and enables traceability from more than one source. Kibble balance experiments offer an effective primary realization method for the new definition of kilogram. Kibble Balance apparatus operating at National Metrology Institute of Turkey is designed with a stationary coil and an oscillating magnet. In contradistinction to traditional moving coil Kibble balance experiments, external magnetic field brings an asymmetry between the Ampere’s law of force and the Faraday’s law of induction in moving magnet experiments. In this paper, we develop a method based on the external magnetic flux density difference measurements in vertical direction to take into account the effect of the external magnetic field on the realization of kilogram. The proposed model in this approach fits well with the data such that the kilogram realization requirement is met within the accuracy of the measuring instrument.

ASSESSMENT OF OSSEOUS DENSITY CHANGES IN PATIENTS WITH MEDICATION-RELATED OSTEONECROSIS OF THE JAWS USING CONE-BEAM CT: A CASE CONTROL STUDY

Objective: In this study, the aim was to analyze density differences in prearranged region of patients with medication-related osteonecrosis of the jaws (MRONJ) and to evaluate potential effected sides in jaws by using cone beam computed tomography (CBCT)Material and Methods: The records of 29 patients diagnosed with MRONJ and under bisphosphonates therapy and examined by CBCT were retrospectively evaluated with age- and gender-matched controls. The gray values (voxel value (VV)) were detected in the maxillary tuberosity (MTs), anterior supporting bone of nasopalatine canal (NPCs), mental foramen regions (MFs), center of symphysis and the bone surrounding the MRONJ area.Results: According to the results, the mostly affected area was the bone under the mental foramen. There were significant differences between MRONJ and controls for right and left MFs (p=0.03, p=0.006 respectively). The mean gray value of right MTs were: 165.04 for controls and 212.4 for patients (p=0.13); left MTs were 208.6 for controls and 268.0 for patients (p=0.32); NPCs were 575.1 for controls and 572.6 for patients (p=0.96); and MSs were 679.2 for controls and 828.2 for patients (p=0.1). The gray value in the inferior peripheral bone of exposed region was the highest.Conclusion: The present study shows that bisphosphonates cause internal morphological changes in jaws. Morphological changes are more frequent in certain parts of the jawbone such as the mental foramen. Gray values obtained by CBCT for quantitative measurements of density differences, can help achieve useful data for prediction of hazardous conditions where MRONJ can occur and how it will progress.

Characteristics of liquid-liquid immiscibility in Al-Bi-Cu, Al-Bi-Si, and Al-Bi-Sn monotectic alloys: Differential scanning calorimetry, interfacial tension, and density difference measurements

Phase separation in ternary monotectic alloys ${({\mathrm{Al}}_{0.345}{\mathrm{Bi}}_{0.655})}_{90}{X}_{10}$ ($X=\mathrm{Cu},\mathrm{Si},\mathrm{Sn}$; wt %) has been investigated. Experimental work included differential scanning calorimetry and measurements of the liquid-liquid $(l\text{\ensuremath{-}}l)$ interfacial tension and difference in densities of coexisting phases. It is established that the interfacial tension between Al-rich and Bi-rich liquid phases increases when either Cu or Si is added and it decreases when Sn is added to the ${\mathrm{Al}}_{34.5}{\mathrm{Bi}}_{65.5}$ binary. This is related to the size of miscibility gap and is explained by increasing composition gradient across the $(l\text{\ensuremath{-}}l)$ interface upon addition of either Cu or Si and its decreasing upon addition of Sn to the Al-Bi binary. The drop of interfacial tension in liquid ${({\mathrm{Al}}_{0.345}{\mathrm{Bi}}_{0.655})}_{90}{\mathrm{Sn}}_{10}$ against ${\mathrm{Al}}_{34.5}{\mathrm{Bi}}_{65.5}$ is also caused by adsorption of Sn at the interface. Temperature dependences of the interfacial tension and density difference in the alloys studied follow a power law in reduced temperature $({T}_{C}\ensuremath{-}T)$ at approach of the critical point with exponents close to the values predicted by the renormalization group theory of critical behavior.

Standard partial molar volumes in water of mono- and polyhydric aliphatic alcohols in wide ranges of temperature and pressure

New results of a systematic study of partial molar volumes at infinite dilution (standard partial molar volumes) in water of several hydroxyderivatives of aliphatic hydrocarbons are summarized. The experiments were performed using an automated vibrating-tube densimeter designed for the measurements of density differences Δ ρ = ρ(solution) − ρ(water) in the temperature range from 298 K to 573 K and at pressures up to 30 MPa. The set of solutes comprises monohydric alcohols derived from methane, ethane, propane, and isomers of butane, and selected polyhydric (from two to five hydroxyl groups) derivatives of ethane, propane, n-butane, n-pentane, 2,2-dimethylpropane and n-hexane. Analogues of isothermal compressibility and isobaric expansivity for standard partial molar volume have also been evaluated from experimental data. The results are discussed from the point of view of regularities within homologous series. The effect of the number of hydroxyl groups and their position on the aliphatic chain is examined. Particular attention is focused to the sign inversion of the derivatives of standard partial molar volume with respect to temperature and pressure that is observed for solutes with large number of hydroxyl groups. A simple group contribution method has proved to be capable to predict this behaviour qualitatively, the effect is not, however, strictly additive.

Comparison of Density Difference Measurements at PTB and NMIJ

Silicon single crystals are used as density standards and to determine the Avogadro constant. Density comparisons by the flotation method can check the homogeneity of the silicon crystals and determine the absolute density of silicon samples by comparison to primary density standards. Results of the two flotation apparatuses at NMIJ (Japan) and PTB (Germany) were compared with each other and with density determinations from other methods. For this purpose, three small silicon samples from the crystals WASO 04 and NRLM4 were measured in both institutes. These measurements show that the flotation method is able to detect and measure density differences with uncertainties of 0.02/spl middot/10/sup -6//spl rho/. Additionally, the density of the 1-kg silicon sphere AVO#1 was determined by flotation comparisons to primary standards of the institutes and compared with density values obtained by different methods. With one exception, all results are consistent within the combined uncertainties, the largest relative density difference being only 0.18/spl middot/10/sup -6/.

Investigating the light absorption in a single pass through the photoreceptor layer by means of the lipofuscin fluorescence

Reflection densitometry has been widely used to measure the density difference of the bleachable cone photopigments in human eyes. Most such measurements make a series of assumptions concerning the amount of scattered light to derive an estimate of the true cone photopigment density from the density difference measurements. The current study made three types of measurements of the light returning from the eye before and after bleaching: the amount of light returning in the “directed” reflection, which is a double-pass estimate of the cone photopigment density; the amount of light in undirected or diffuse reflection; and the amount of fluorescence from lipofuscin in the RPE, which provides a single-pass measurement of optical density difference. For a 1 deg foveally fixated field, the density difference estimates for the three measurements were 0.68, 0.21, and 0.22 respectively. The lipofuscin fluorescence was found to be unguided. The background density difference was non-negligible and very close to the single pass estimate from fluorescence. These measurements each involve potentially different pathways of light through the retina, and therefore place different constraints on models of these pathways. A simple model comparing the directional and the fluorescence optical densities produced retinal coverage estimates around 70–75%. Estimates of the shape factor of the single pass optical Stiles–Crawford effect were evaluated from the dark-adapted and bleached fluorescence measurements. The values were closer to those obtained from psychophysical methods than to the double pass optical Stiles–Crawford shape factors obtained directly from retinal reflectometry.

A vibrating tube flow densitometer for measurements with corrosive solutions at temperatures up to 723 K and pressures up to 40 MPa

A new version of a vibrating tube flow densitometer has been designed permitting measurements of density differences between two fluids in the temperature range from 298 to 723 K and at pressures up to 40 MPa. The instrument is equipped with a Pt/Rh20 vibrating tube (1.6-mm o.d.) and a Pt/Rh10 transporting tube (1.2-mm o.d.) permitting measurements with highly corrosive liquids. The period of oscillation of the tube is about 7.5 ms, with a typical stability better than 10−4% over about a 1-h period over the entire temperature interval. The calibration constantK at room temperature is about 530 kg·m−3·ms−2, with a temperature coefficient of approximately −0.13kg·m−3·ms−2·K−1, and is practically pressure independent. It can be determined by calibration with a reproducibility generally better than 0.1%. The instrument was tested with NaCl(aq) solutions in the temperature range from 373 to 690 K for density differences between sample and reference liquid ranging from 200 to 2 kg·m−3; the corresponding errors are believed to be below 0.3 and 5%, respectively. A highly automated temperature control maintains the temperature of the tube stable to within ±0.02 K.

Reflectometry with a scanning laser ophthalmoscope

We describe noninvasive techniques to optimize reflectometry measurements, particularly retinal densitometry, which measures the photopigment density difference. With these techniques unwanted scattered light is greatly reduced, and the retina is visualized during measurements. Thus results may be compared for each retinal location, and visible artifacts are minimized. The density difference measurements of the cone photopigment depend on the optical configuration of the apparatus. The cone photopigment density difference is greatest near the fovea and for most observers decreases rapidly with eccentricity. A research version for reflectometry and psychophysics of the scanning laser ophthalmoscope is described.

Neutron density difference measurements for 26,24Mg and 36,34,32S using low-energy pions

The elastic scattering differential cross-section ratios of 36S/ 32S, 34S/ 32S and 26Mg/ 24Mg have been measured with 48.4 MeV and 43.9 MeV negative pions, respectively, using magnetic spectrometers. The data are analysed with optical potential calculations, using a Fourier-Bessel description for the neutron density of the heavier isotope. Neutron density and rms radius differences between the isotopes are determined and compared to shell-model calculations, and show reasonable agreement.

A Maturity Index for Blueberries Using Light Transmittance1

Abstract Light transmittance curves of intact blueberries, ‘Wolcott’ and ‘Bluecrop’ cul-tivars4, were recorded in the visible and infrared with the ASCO Biospect5 and correlated with anthocyanin content. Correlation coefficients were computed for a large number of possible maturity indexes to determine the optimum index. In all cases the index involves the measurement of the optical density of the intact fruit at 2 wavelengths and computation of the optical density difference. From the ‘Wolcott’ blueberry correlation data, the highest correlations, 0.925 and 0.967, were found in the infrared region between ∆OD(760–800 nm) vs anthocyanin content per berry and between ∆OD(760–800 nm) vs anthocyanin content per g fresh weight of tissue, respectively. For the ‘Bluecrop’ blueberry, the highest correlations, 0.933 and 0.916, were found in the infrared region between ∆OD(740–800 nm) vs anthocyanin content per berry and between ∆OD(740–800 nm) vs anthocyanin content per g fresh weight of tissue, respectively. Thus, optical density difference measurements of individual intact fruits afford a reliable maturity index for blueberries.