Apparent Dependence Research Articles

Velocity circulation intermittency in finite-temperature turbulent superfluid helium

We investigate the intermittent behavior of velocity circulation statistics in quantum turbulence. We perform grid turbulence experiments in superfluid helium and numerical simulations of the two-fluid Hall-Vinen-Bekarevich-Khalatnikov (HVBK) model to show that the scaling properties of circulation moments are compatible with classical turbulence. We also show that there is no apparent temperature dependence on the intermittent behavior of the turbulent superflow.

Cation Short-Range Ordering of MgAl2O4 and NiAl2O4 Spinel Oxides at High Temperatures via In Situ Neutron Total Scattering.

Complex oxides that adopt the isometric spinel structure (AB2O4) are important for numerous technological applications and are relevant for certain geological processes, which involve exposure to extreme environments such as high pressures and temperatures. Recent studies have shown that the changes to the spinel structure caused by these environments are complex and depend on the material length scale under consideration. In this study, we have expanded this approach to the behavior of spinels under high temperatures. In situ neutron total scattering experiments, coupled with pair distribution function analysis, performed on two spinel compositions with various levels of pre-existing disorder (MgAl2O4 and NiAl2O4) revealed that both compositions trend to a state of maximum disorder where the A and B cations are randomly distributed among the two available sites. Temperature-induced cation inversion, conventionally understood as an exchange of cations on the A and B sites, is locally expressed as an atomic rearrangement to a tetragonal symmetry, a correlation that is retained up to the maximum temperature studied (1000 °C). A complex thermal expansion behavior is revealed wherein the oxide materials expand heterogeneously at the level of coordination polyhedra with an apparent dependence on bond strength.

Thermophysical properties of Ti-6Al-4V fabricated by powder bed fusion methods

Three types of Ti-6Al-4V alloys were prepared by powder bed fusion methods using a laser powder bed fusion ( L -PBF) and two different electron-beam powder bed fusion (E-PBF) systems. The specific heat capacity, linear thermal expansion, and thermal diffusivity were measured from room temperature to ~ 1000 °C. The thermal conductivity values were calculated using the above values. The thermal diffusivity values of all samples along the build direction are similar and a few percent higher than those perpendicular to the build direction. The effect of measurement direction on the linear thermal expansion is evident and related to the processing conditions. A correction for the effect of low porosity (<1%) on thermal diffusivity and thermal conductivity shows that regardless of production method, the porosity corrected values are close for all the PBF samples. Attempts were made to correlate the subtle differences between the samples to the oxygen content, microstructure processing route, and preferred orientation. In the E-PBF samples with a lower cooling rate during production, thermal expansion and thermal diffusivity were nearly isotropic. The subtle changes between the E-PBF samples in both directions directly correlate to a preferred orientation parameter, the peak intensity ratio I (002) α /I (101)α . These results were compared to both cast and additive manufacturing literature, and differences were discussed. • Slight differences exist in L\E-PBF samples’ thermal expansions in both directions. • Anisotropy of the thermal diffusivity exists for both L-\E-PBF samples. • Apparent dependence on grain size exists in thermal diffusivity for various samples. • A dependency on O content was found in E-PBF’s thermal expansion and diffusivity. • A relationship was found between the thermal diffusivity and I (002)α /I (101)α ratio.

Assessment of organochlorine pesticides in the atmosphere of South Korea: spatial distribution, seasonal variation, and sources.

Organochlorine pesticides (OCPs) are widely used in certain countries. We determined atmospheric concentrations, distribution patterns, and seasonal variations of OCPs at four sites in South Korea for 1year. Samples of 22 OCPs were collected using a high-volume air sampler, and measured via the isotope dilution method with HRGC/HRMS. In South Korea, pentachlorobenzene (PeCB), hexachlorocyclohexane (HCB), and endosulfan (EnSF) were dominant, accounting for > 87% of total OCPs. Spatial distributions showed significant differences and the highest levels were observed in Seosan (295.2pg·m-3), indicating the compounding potential of diverse sources as Seosan has concentrated large-scale industrial complexes and agricultural activity (Seoul: 243.6pg·m-3 > Jeju: 193.5pg·m-3 > Baengnyeong: 178.2pg·m-3). The isomeric ratios of OCPs in the South Korean atmosphere indicated that the dominant sources of HCB and dichlorodiphenyltrichloroethane were primarily used in the past; meanwhile, chlordane (CHL) and EnSFs were derived from recent material inputs. Seasonally, OCP concentrations largely peaked in summer with minimum values in winter. This apparent temperature dependence suggests the re-volatilization of accumulated chemicals into the atmosphere. Additionally, an air mass back trajectory indicated the influence of pollutants released from a reservoir through long-range atmospheric transport in the summer. In particular, restricted OCPs are primarily released into the atmosphere by inadvertent sources, such as industrial activities and volatilization from contaminated areas. Thus, severe OCP pollution in Korea is due to the mobile nature of the particles. These data can be useful for the continuous monitoring of long-range transported air pollutants that are transferred between countries.

Comparative kinetics study of the catalytic oxidation of benzene and its mono-halogenated derivatives over V 2 O 5 –WO 3 /TiO 2 catalyst

The SCR-DeNOx commercial catalysts are reported as possible candidates to remove aromatic VOCs and NO x simultaneously. In this paper, we present the kinetic studies of the oxidation of benzene and its mono-halogenated derivatives over V 2 O 5 –WO 3 /TiO 2 catalyst as typical high-dust SCR-DeNOx system. The kinetic investigation follows the influence of temperature on the conversion of aromatic VOCs to establish the apparent energy activation and dependence on between temperature and the effective constant rate of the catalytic oxidation reaction. The data shows that the catalytic oxidation process takes place after a combined kinetic mechanism, mass transport through pores—chemical transformation.

Nonlocal model of electromechanical fields and effective properties of piezoelectric materials with rigid and electrically conductive inclusions

A rigid and electrically conductive line inclusion (or electrode) in piezoelectric materials is considered under the framework of nonlocal effects for the stress and electric displacement fields. Both the piezoelectric medium and the inclusion are of finite size. The poling direction of the piezoelectric medium and the plane of inclusion are parallel. Electromechanical fields and the equivalent values of the elastic modulus, piezoelectric constants and dielectric constants along the inclusion direction are evaluated. The effect of the nonlocal parameter of the piezoelectric material is particularly remarkable for the stress and electric displacement fields. The maximum stress and electric displacement close the inclusion tip reduce as the nonlocal effect of the medium become stronger. However, the effective electromechanical properties of the piezoelectric medium do not have an apparent dependence on the nonlocal effect.

Phase Volume Fraction-Dependent Strengthening in a Nano-Laminated Dual-Phase High-Entropy Alloy.

A recently synthesized FCC/HCP nano-laminated dual-phase (NLDP) CoCrFeMnNi high entropy alloy (HEA) exhibits excellent strength–ductility synergy. However, the underlying strengthening mechanisms of such a novel material is far from being understood. In this work, large-scale atomistic simulations of in-plane tension of the NLDP HEA are carried out in order to explore the HCP phase volume fraction-dependent strengthening. It is found that the dual-phase (DP) structure can significantly enhance the strength of the material, and the strength shows apparent phase volume fraction dependence. The yield stress increases monotonously with the increase of phase volume fraction, resulting from the increased inhibition effect of interphase boundary (IPB) on the nucleation of partial dislocations in the FCC lamella. There exists a critical phase volume fraction, where the flow stress is the largest. The mechanisms for the volume fraction-dependent flow stress include volume fraction-dependent phase strengthening effect, volume fraction-dependent IPB strengthening effect, and volume fraction-dependent IPB softening effect, that is, IPB migration and dislocation nucleation from the dislocation–IPB reaction sites. This work can provide a fundamental understanding for the physical mechanisms of strengthening effects in face-centered cubic HEAs with a nanoscale NLDP structure.

Multivariate model-based investigation of the temperature dependence of ozone concentration in Finnish boreal forest

Tropospheric ozone (O3) concentrations are observed to increase with temperature in urban and rural locations. We investigated the apparent temperature dependency of daytime ozone concentration in the Finnish boreal forest in summertime based on long-term measurements. We used statistical mixed effects models to separate the direct effects of temperature from other factors influencing this dependency, such as weather conditions, long-range transport of precursors, and concentration of various hydrocarbons. The apparent temperature dependency of 1.16 ppb °C−1 based on a simple linear regression was reduced to 0.87 ppb °C−1 within the canopy for summer daytime data after considering these factors. In addition, our results indicated that small oxygenated volatile organic compounds may play an important role in the temperature dependence of O3 concentrations in this dataset from a low-NOx environment. Summertime observations and daytime data were selected for this analysis to focus on an environment that is significantly affected by biogenic emissions. Despite limitations due to selection of the data, these results highlight the importance of considering factors contributing to the apparent temperature dependence of the O3 concentration. In addition, our results show that a mixed effects model achieves relatively good predictive accuracy for this dataset without explicitly calculating all processes involved in O3 formation and removal.

Constraining a model of punctuated river incision for Quaternary strath terrace formation

In the small fraction of Earth's surface with the highest erosion rates such as the Alps and Himalayas quantifying rates of incision, rock uplift and inferring climatic controls on the landscape can be relatively straightforward once the ages of river terraces cut in bedrock (strath terraces) are constrained. However, in many mid to lower relief settings that are more typical of mountain belts worldwide, periods of net river incision and riverbed lowering are relatively short (punctuated), interrupted by long periods of sediment aggradation or stasis. We define a conceptual model of punctuated river incision and strath terrace formation for the calculation of incision and rock uplift rates, and recommend strategies for geochronological sampling and interpretation. An approach using OSL dating of terrace gravels allows us to constrain a detailed ~150 kyr history of punctuated river incision and strath terrace formation spanning two stratigraphic landform levels in the High Atlas Mountains (NW Africa). Extensive preservation and exposure of strath-top gravels, within a post-orogenic setting unaffected by eustatic influences, enables the derivation of rates of base-level fall, integrated over periods of strath-top aggradation and incision, that are consistent with independently constrained regional rock uplift rates. Combining a punctuated river incision model with our well-constrained terrace formation history allows us to demonstrate how assumptions concerning Quaternary river incision and aggradation can lead to the problematic Sadler Effect, an apparent dependence of incision rates on measured time interval. Subsequently, we demonstrate that an approach to reinterpreting previously published data using the punctuated incision model, even when combined with limited terrace age data, results in more consistent conclusions about rates of river incision, rock uplift and base-level lowering across the mountain belt. Our recommendations for sampling strategies to constrain rock uplift rates require samples to be taken just above the strath surface, and in addition towards the top of the deposit for river incision rates. In a setting with punctuated river incision and strath terrace formation, both rock uplift and incision rates require burial dates, as exclusive use of abandonment ages will not yield constraints on accurate rates of rock uplift or incision. Furthermore, we find that only with multiple along-stream locations and multiple burial dates in each terrace deposit, could a reliable climatic signal be extracted: this signal would not have shown up in terrace abandonment ages such as those derived from cosmogenic exposure dates. The demonstrated effects of assumptions about strath terrace formation, and the recommended approaches for sampling and interpretation, have implications for those attempting to constrain palaeoclimatic, tectonic, and geomorphic histories from strath terrace records in regions exhibiting punctuated river incision.

Dominant geometrical factors of collective cell migration in flexible 3D gelatin tube structures

Collective cell migration is a dynamic and interactive behavior of cell cohorts essential for diverse physiological developments in living organisms. Recent studies have revealed the importance of three-dimensional (3D) topographical confinements to regulate the migration modes of cell cohorts in tubular confinement. However, conventional in vitro assays fail to observe cells’ behavior in response to 3D structural changes, which is necessary for examining the geometric regulation factors of collective migration. Here, we introduce a newly developed assay for fabricating flexible 3D structures of capillary microtunnels to examine the behavior of vascular endothelial cells (ECs) as they progress through the successive transition across wide or narrow tube structures. The microtunnels with altered diameters were formed inside gelatin-gel blocks by photo-thermal etching with micrometer-sized spot heating of the focused infrared laser absorption. The ECs migrated and spread two-dimensionally on the inner surface of gelatin capillary microtunnels as a monolayer instead of filling the entire capillary. In the straight cylindrical topographical constraint, leading ECs exhibited no apparent diameter dependence for the maximum peak migration velocity. However, widening the diameter in the narrow-wide structures caused a decrease in migration velocity following in direct proportion to the diameter increase ratio, whereas narrowing the diameter in wide-narrow microtunnels increased the speed without obvious correlation between velocity change and diameter change. The results demonstrated the ability of the newly developed flexible 3D gelatin tube structures for collective cell migration, and the findings provide insights into the dominant geometric factor of the emerging migratory modes for endothelial migration as asymmetric fluid flow-like behavior in the borderless cylindrical cell sheets.

Understanding the factors affecting contact resistance in nanowire field effect transistors (NWFETs) to improve nanoscale contacts for future scaling

In this paper, dry etched vertical nanowires (VNWs) are used in transmission line/transfer length analysis to study the contacts of gate-all-around devices for future technology nodes. VNW resistors with Mo and Pd based metal stack contacts to p-InGaAs show Schottky behavior, unlike the planar counterpart. The resistance for Mo contact is higher than Pd, however, Pd was found to form an alloy with InGaAs at temperatures as low as 190 °C, and the length of Pd diffusion into the InGaAs increased at smaller NW dimensions, hindering future scalability. The minimum extracted specific contact resistivity (ρC) values are 1.6 × 10−5 Ω cm2 (Mo) and 4.2 × 10−6 Ω cm2 (Pd) for a doping level of 1 × 1019 cm−3. An apparent dependence of ρC on the NW diameter was also observed. This has been attributed to the surface states under the un-gated region of NW devices and found to dominate at smaller diameters. An analytical model to account for such geometrical effects has also been developed and validated with technology computer-aided design simulations. The analysis presented in this paper effectively captures the 3D aspects of an NW contact at nanoscale dimensions and can be applied irrespective of the semiconductor and contact metal used.

Conformally-rescaled Schwarzschild metrics do not predict flat galaxy rotation curves

For conformally invariant gravity theories defined on Riemannian spacetime and having the Schwarzschild–de-Sitter (SdS) metric as a solution in the Einstein gauge, we consider whether one may conformally rescale this solution to obtain flat rotation curves, such as those observed in galaxies, without the need for dark matter. Contrary to recent claims in the literature, we show that if one works in terms of quantities that can be physically measured, then in any conformal frame the trajectories followed by ‘ordinary’ matter particles are merely the timelike geodesics of the SdS metric, as one might expect. This resolves the apparent frame dependence of physical predictions and unambiguously yields rotation curves with no flat region. We also show that attempts to model rising rotation curves by fitting the coefficient of the quadratic term in the SdS metric individually for each galaxy are precluded, since this coefficient is most naturally interpreted as proportional to a global cosmological constant. We further extend our analysis beyond static, spherically-symmetric systems to show that the invariance of particle dynamics to the choice of conformal frame holds for arbitary metrics, again as expected. Moreover, we show that this conclusion remains valid for conformally invariant gravity theories defined on more general Weyl–Cartan spacetimes, which include Weyl, Riemann–Cartan and Riemannian spacetimes as special cases.

Collisional electron paramagnetic resonance frequency shifts in Cs-Rb-Xe mixtures

We report a measurement of the ratio of dimensionless enhancement factors ${\ensuremath{\kappa}}_{0}$ for $\mathrm{Cs}\text{\ensuremath{-}}^{129}\mathrm{Xe}$ and $\mathrm{Rb}\text{\ensuremath{-}}^{129}\mathrm{Xe}$ in the temperature range 115--140 ${}^{\ensuremath{\circ}}\mathrm{C}$; both pairs are used in spin-exchange optical pumping (SEOP) to produce hyperpolarized $^{129}\mathrm{Xe}$. ${\ensuremath{\kappa}}_{0}$ characterizes the amplification of the $^{129}\mathrm{Xe}$ magnetization contribution to the alkali-metal electronic effective field, compared to the case of a uniform continuous medium in classical magnetostatics. The measurement was carried out in ``hybrid'' vapor cells containing both Rb and Cs metal in a prescribed ratio, producing approximately the same vapor density for both. Alternating measurements of the optically detected electron paramagnetic resonance (EPR) frequency shifts caused by the SEOP polarization and subsequent sudden destruction of the same quantity of $^{129}\mathrm{Xe}$ magnetization were made for $^{133}\mathrm{Cs}$ and either $^{87}\mathrm{Rb}$ or $^{85}\mathrm{Rb}$. An important source of systematic error caused by power fluctuations in the pump laser that produced variable light shifts in the EPR frequency was characterized and then mitigated by allowing sufficient warm-up time for the pump laser. We measured ${({\ensuremath{\kappa}}_{0})}_{\mathrm{CsXe}}/{({\ensuremath{\kappa}}_{0})}_{\mathrm{RbXe}}=1.215\ifmmode\pm\else\textpm\fi{}0.007$ with no apparent temperature dependence. Based on our previous measurement ${({\ensuremath{\kappa}}_{0})}_{\mathrm{RbXe}}=518\ifmmode\pm\else\textpm\fi{}8$, we determine ${({\ensuremath{\kappa}}_{0})}_{\mathrm{CsXe}}=629\ifmmode\pm\else\textpm\fi{}10$, which is more precise than, but consistent with, a previous measurement made by J. Fang et al. [Chin. Phys. B 23, 063401 (2014)].

Spatiotemporal Variability of Earthquake Source Parameters at Parkfield, California, and Their Relationship With the 2004 M6 Earthquake

AbstractEarthquake stress drop is an important source parameter that directly links to strong ground motion and fundamental questions in earthquake physics. Stress drop estimations may contain significant uncertainties due to such factors as variations in material properties and data limitations, which limit the applications of stress drop interpretations. Using a high‐resolution borehole network, we estimate stress drop for 4551 (M0‐4) earthquakes on the San Andreas Fault at Parkfield, California, between 2001 and 2016 using spectral decomposition and an improved stacking method. To evaluate the influence of spatiotemporal variations of material properties on stress drop estimations, we apply different strategies to account for spatial variations of velocity and attenuation changes, and divide earthquakes into three separate time periods to correct temporal variations of attenuation. These results show that appropriate corrections can significantly reduce the scatter in stress drop estimates, and decrease apparent depth and magnitude dependence. We find that insufficient bandwidth can cause systematic underestimation of stress drop estimates and increased scatter. The stress drop measurements from the high‐frequency borehole recordings exhibit complex stable spatial patterns with no clear correlation with the nature of fault slip, or the slip distribution of the 2004 M6 earthquake. Temporal variations are significantly smaller, less well resolved and varying spatially. They do not affect the long‐term stress drop spatial variations, suggesting local material properties may control the spatial heterogeneity of stress drop.

In vitro evaluation suggests fenfluramine and norfenfluramine are unlikely to act as perpetrators of drug interactions.

Studies support the safety and efficacy of fenfluramine (FFA) as an antiseizure medication (ASM) in Dravet syndrome, Lennox‐Gastaut syndrome, or CDKL5 deficiency disorder, all pharmacoresistant developmental and epileptic encephalopathies. However, drug–drug interactions with FFA in multi‐ASM regimens have not been fully investigated. We characterized the perpetrator potential of FFA and its active metabolite, norfenfluramine (nFFA), in vitro by assessing cytochrome P450 (CYP450) inhibition in human liver microsomes, CYP450 induction in cultured human hepatocytes, and drug transporter inhibition potential in permeability or cellular uptake assays. Mean plasma unbound fraction was ~50% for both FFA and nFFA, with no apparent concentration dependence. FFA and nFFA were direct in vitro inhibitors of CYP2D6 (IC50, 4.7 and 16 µM, respectively) but did not substantially inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, or CYP3A4/5. No time‐ or metabolism‐dependent CYP450 inhibition occurred. FFA and nFFA did not induce CYP1A2; both induced CYP2B6 (up to 2.8‐fold and up to 2.0‐fold, respectively) and CYP3A4 (1.9‐ to 3.0‐fold and 3.6‐ to 4.8‐fold, respectively). Mechanistic static pharmacokinetic models predicted that neither CYP450 inhibition nor induction was likely to be clinically relevant at doses typically used for seizure reduction (ratio of area under curve [AUCR] for inhibition <1.25; AUCR for induction >0.8). Transporters OCT2 and MATE1 were inhibited by FFA (IC50, 19.8 and 9.0 μM) and nFFA (IC50, 5.2 and 4.6 μM) at concentrations higher than clinically achievable; remaining transporters were not inhibited. Results suggest that FFA and nFFA are unlikely drug–drug interaction perpetrators at clinically relevant doses of FFA (0.2−0.7 mg/kg/day).

The study of the impact of the developed metallurgical industry on the population health in the industrial centre

Introduction. The metallurgical enterprises of the city of Lipetsk are city-forming and provide the main anthropotechnogenic burden on the health of the population. The priority of preserving the health of the population determines the importance of studying the determinants of the environment on the health of the population and creates conditions for the organization of scientific research, which are aimed at developing scientifically based recommendations to reduce this process. The purpose of the study is to identify the features of the formation of the prevalence of non-communicable diseases in an industrial centre with a developed metallurgical industry. Material and methods. We used the data of the regional information fund concerning the state of the human environment and public health, the materials of the consolidated volume of maximum permissible emissions (MAE) of the city of Lipetsk, and statistical data. The comparative non-carcinogenic hazard indices and the assessment of mass non-communicable morbidity thresholds were calculated. Results. The analysis showed that as a result of the implementation of environmental measures at the city’s enterprises, there was a significant decrease in the level of atmospheric pollution. Positive changes in the habitat state are confirmed by the incidence rate for individual nosological units. A conjugated analysis of the indices of comparative non-carcinogenic hazard and morbidity made it possible to establish a threshold for mass non-infectious morbidity by nosology for the adult population and children. Discussion. The incidence rate has also dropped significantly. The improved quality of atmospheric air has erased the apparent dependence of the level and structure of morbidity from the impact of metallurgical production alone. Conclusion. Despite the decrease in emissions from stationary sources due to technological re-equipment, the implementation of environmental measures, and the incidence of many nosologies, many problems remain unsolved.

Production of strange hadrons in jets and underlying events in pp and p–Pb collisions with ALICE

The production of strange (, Λ) and multi-strange (Ξ± and Ω±) hadrons in jets and underlying events in pp and p–Pb collisions is studied with ALICE at the LHC. Transverse momentum (p T) differential density distribution of particles produced in a jet is compared to that of inclusive particle production and that in underlying events. The particle yield ratios of and as a function of p T are also investigated in jets and underlying events. The production of the multi-strange hadrons, Ξ± and Ω±, and the corresponding ratio in jets and underlying events are measured for the first time. The p T-differential density distribution of hadrons associated with hard scattering decreases slower than that for inclusive production. The baryon-to-meson and baryon-to-baryon ratios measured in jets exhibit clear differences from values obtained from the inclusive spectra in the intermediate p T range. The p T distribution of strange hadrons produced in jets is also studied in pp collisions at and and in p–Pb collisions at . The p T spectra of particle produced in jets are independent of collision systems and collision energies. No apparent collision energy and collision system dependence is observed for the particle yield ratios of and associated with energetic jets. These new results are compared to PYTHIA 8 event generator. The ratio are generally reproduced by the model, but large discrepancies between data and PYTHIA simulations are observed for .

Development of the Concurrent Multiscale Discrete-Continuum Model and Its Application in Plasticity Size Effect

A concurrent multiscale model coupling discrete dislocation dynamics to the finite element method is developed to investigate the plastic mechanism of materials at micron/submicron length scales. In this model, the plastic strain is computed in discrete dislocation dynamics (DDD) and transferred to the finite element method (FEM) to participate in the constitutive law calculation, while the FEM solves the complex boundary problem for DDD simulation. The implementation of the whole coupling scheme takes advantage of user subroutines in the software ABAQUS. The data structures used for information transferring are introduced in detail. Moreover, a FE mesh-based regularization method is proposed to localize the discrete plastic strain to continuum material points. Uniaxial compression tests of single crystal micropillars are performed to validate the developed model. The results indicate the apparent dependence of yield stress on sample size, and its underlying mechanisms are also analyzed.

Sintering, hardness and cation inversion of nanocrystalline Beryllium – Magnesium aluminate ceramics

Beryllium-magnesium aluminate (Be0.1Mg0.9Al2O4 and Be0.2Mg0.8Al2O4) nanoparticles are synthesized by a coprecipitation method and sintered using Spark Plasma Sintering (SPS) to achieve near full density ceramics with grain sizes at the nanoscale. The sintered nanoceramics display grain sizes ranging from 14 to 33 nm, which are analyzed for optical transmission, Vickers hardness, and cation site inversion. When compared to Be-free MgAl2O4 nanoceramics, both Be0.1Mg0.9Al2O4 and Be0.2Mg0.8Al2O4 show transmissions ∼30% lower at wavelength in the infrared range. The samples show a Vickers hardness of ∼19.2 GPa with no apparent dependence on grain size. These values are consistently lower to those reported for beryllium-free MgAl2O4 spinel with similar grain size. 27Al and 9Be Nuclear Magnetic Resonance (NMR) spectroscopy reveals that beryllium does not have a significant effect on cationic site inversion in the spinel and, similar to beryllium-free MgAl2O4, inversion remains solely a function of grain size. The results indicate beryllium ions form solid-solutions with MgAl2O4 spinel structure and do not alter the grain boundaries significantly enough to influence the mechanical properties of nanocrystalline ceramics.

Conversion from dose length product to effective dose for the CT component of whole-body PET/CT.

For dose management of CT, the ratio of effective dose (ED) to dose length product (DLP) is often used to convert DLP to ED. We evaluated this ratio in the CT component of whole-body PET/CT performed under various imaging conditions to determine a practical method for ED estimation applicable to PET/CT. In total, 400 patients who underwent whole-body PET/CT were enrolled. The imaging conditions were variable in terms of the scanner model, setting of automatic exposure control (AEC) setting and arm positioning. The scan range was divided into six anatomical regions. DLP was calculated for each region, and multiplied by the conversion factor for the respective region to determine regional ED. The six regional EDs were summed together to determine ED by the regional DLP method (EDrDLP). Additionally, regional ED was assessed using CT-Expo, software dedicated to CT dose estimation, and the total of six regional EDs were defined as ED by the CT-Expo method (EDCT-Expo). EDrDLP/DLP and EDCT-Expo/DLP were calculated using DLP automatically provided by the scanner. EDrDLP/DLP ranged from 0.0121 to 0.0128mSv/mGy/cm with the arms up and from 0.0127 to 0.0134mSv/mGy/cm with the arms down. Putting the arms down slightly increased EDrDLP/DLP, presumably due to an increased contribution of the chest and abdomen to total radiation exposure. The AEC setting and scanner model also influenced EDrDLP/DLP significantly but slightly. EDCT-Expo/DLP showed apparent scanner dependence, which appeared mainly attributable to differences in the constants used for DLP calculation between the scanner and CT-Expo. Multiplication of scanner-derived DLP by a conversion factor of 0.013mSv/mGy/cm provides acceptable ED estimates.