DT Values Research Articles

Correlation between atomic diffusivity and densification mechanism during spark plasma sintering of titanium alloy powders

In this study, the correlations between the shrinkage behavior, densification mechanism, and atomic diffusivity of the atomized and milled Ti-based crystalline alloy powders are investigated. The densification mechanism of each stage was identified by determining the evolution of the characteristic microstructures at different sintering temperatures in combination with the shrinkage behavior. Importantly, a theoretical framework is established here and elaborate how it can be used to determine the value of the atomic diffusivity DT and a factor g by integrating the interior (related to material properties) and exterior (related to the sintering parameters) variables. This approach can be utilized to provide insights into the active densification mechanisms during spark plasma sintering (SPS). Furthermore, the densification behavior and microstructure evolution of the two types of heat-treated Ti-based alloy powders fabricated by gas atomization and ball milling are compared to validate the framework for different pressures (15, 30, 45, and 60 MPa) and heating rates (30, 60, 90, and 120 K/min). The results indicate that the comprehensive factor g and the atomic diffusivity DT can be used to describe the densification mechanism and thus the shrinkage behavior during each densification stage. Our results provide quantitative proof that the applied pressure and heating rate promote diffusivity to accelerate powder densification during SPS.

Peak bordering for ultrafast single particle analysis using ICP-MS

The characterisation of inorganic nanoparticles (NPs) by single particle inductively coupled plasma mass spectroscopy is possible only if the spectrometer is capable of measurement with high time-signal resolution. The latest generation of spectrometers allow for measurements with dwell times (dt) shorter than the 100 μs gold standard, i.e. as low as 10 μs. The statistical behaviours of signals obtained with dt values of 10, 20, 50, and 100 μs were tested for 40, 60, and 100 nm silver NPs. Very low measured signals (units of counts) led to the occurrence of zero signal values inside the peaks corresponding to individual NPs. The probability of the occurrence of a zero signal inside the peak increased with decreasing dt and decreasing NP size. The standard approach to the bordering of the beginning and end of the peak by one zero signal point failed here and lead to the false detection of a larger number of smaller peaks. For example, in the case of 40 nm NPs a quadruple number of peaks were detected for a dt value of 10 μs compared to the 100 μs dt value; the mean peak width at 10 μs dt was approximately 220 μs, while at 100 μs dt it was 550 μs. The results tended to be less distorted when dt was longer and the NP size was larger. Low dt values also led to a distortion of the peak area distribution. For 40 nm NPs and 10 μs, the most frequent peak area and the width of the peak area distribution were not evaluated due to a non-Gaussian course; 20 μs dt caused (compared to 100 μs) a decrease in the most frequent peak area by approximately 35% (33 counts for 100 μs dt vs. 22 counts for 20 μs dt) and an increase in the width of the peak area distribution by 70% (10 counts for 100 μs dt vs. 17 counts for 20 μs dt). Therefore, new approaches to bordering peaks were tested, which consisted of searching for an uninterrupted zero signal point sequence with a total length of 50 μs or 100 μs. Only the criterion of a 100 μs delay between the two adjacent peaks resulted in values of the number of detected peaks, the most frequent peak areas, and the width of peak area distribution virtually independent of dt.

Comparison of Three Radiobiological Models in Stereotactic Body Radiotherapy for Non-Small Cell Lung Cancer.

Objective: The applicability of the linear quadratic (LQ) model to local control (LC) modeling after hypofractionated radiotherapy to treat lung cancer is highly debated. To date, the differences in predicted outcomes between the LQ model and other radiobiological models, which are characterized by additional dose modification beyond a certain transitional dose (dT), have not been well established. This study aims to compare the outcomes predicted by the LQ model with those predicted by two other radiobiological models in stereotactic body radiotherapy (SBRT) for non-small cell lung cancer (NSCLC).Methods: Computer tomography (CT) simulation data sets for 20 patients diagnosed with stage Ⅰ primary NSCLC were included in this study. Three radiobiological models, including the LQ, the universal survival curve (USC) and the modified linear quadratic and linear (mLQL) model were employed to predict the tumor control probability (TCP) data. First, the dT values for the USC and mLQL models were determined. Then, the biologically effective dose (BED) and the predicted TCP values from the LQ model were compared with those calculated from the USC and mLQL models.Results: The dT values from the USC model were 29.6 Gy, 33.8 Gy and 44.5 Gy, whereas the values were 90.2 Gy, 84.0 Gy and 57.3 Gy for the mLQL model for 1-year, 2-year and 3-year TCP prediction. The remarkable higher dT values obtained from the mLQL model revealed the same dose-response relationship as the LQ model in the low- and high-dose ranges. We also found that TCP prediction from the LQ and USC models differed by less than 3%, although the BED values for the two models were significantly different.Conclusion: Radiobiological analysis reveals small differences between the models and suggested that the LQ model is applicable for modeling LC using SBRT to treat lung cancer, even when an extremely high fractional dose is used.

Oral Health in Polish Fifteen-year-old Adolescents.

To assess caries prevalence and periodontal condition in adolescents in Poland and investigate the factors related to oral health. A national survey was carried out among 615 15-year-olds of both sexes living in urban and rural areas. Subjects were selected via cluster sampling. The mean DMFT and its components, the tooth distribution pattern of caries and percentage of subjects with gingival bleeding and gingival pockets were analysed. The information regarding sociodemographic, oral hygiene and nutritional variables was collected via questionnaire to evaluate their relationships with caries and periodontal parameters. The t-test, bivariate and multivariate logistic analyses were conducted to evaluate the differences and dependent variables of caries prevalence and gingivitis. Caries prevalence was 94.0%, and DMFT was 5.75 ± 3.74. Higher DMFT, DT and MT values were found in rural areas. 50% of the subjects carried about 75% of the total caries burden. Severe caries (DMFT ≥7) was associated with toothbrushing less than twice a day, not using a fluoridated dentifrice, frequent consumption of snacks and absence of pit-and-fissure sealants. The prevalence of gingival bleeding was 37.4% and shallow pockets 2.8%, which were higher in males and rural areas. Gingival bleeding was associated with toothbrushing less than a twice a day, not using dental floss and consumption of fresh fruits and vegetables less than once a week. The prevalence of oral diseases in Poland is very high. Additional strategies must be implemented to promote oral health early on to improve oral hygiene practices and nutritional habits.

Surface properties and solubility enhancement of Gemini/conventional surfactant mixtures based on sulfonate Gemini surfactant

The synergistic effect of sulfonate Gemini surfactant (SGS12) with different kinds of conventional surfactants on surface properties and solubility enhancement was investigated. Results indicated that the absolute values of βm were in the following order: SGS12/BQAS > SGS12/DTAB > SGS12/rhamnolipid > SGS12/SDS > SGS12/Triton X-100. The cationic/anionic surfactant mixtures formed micelles at a low concentration, which resulted from the strong attraction among different charged hydrophilic headgroups. Moreover, the molar solubilization ratio and lnKm values indicated that the solubility of SGS12/BQAS, SGS12/Triton X-100, and SGS12/DTAB mixtures toward pyrene was higher than that of either component. The micelle's hydrodynamic sizes of cationic/anionic surfactant mixtures were larger than that of either component, so the hydrophobic space to dissolve additional pyrene was large. Furthermore, dynamic surface tension determination suggested that cationic/anionic surfactant mixtures had a relatively short induction period, and the n values for SGS12/BQAS and SGS12/DTAB mixtures were slightly larger than those for either component. At the total surfactant concentration of 1 μmol·L−1, the plots of γt versus t1/2 for all surfactant mixtures were linear, indicating that the initial adsorption was controlled by diffusion. The values of Dt→0 for SGS12/BQAS, SGS12/DTAB, and SGS12/rhamnolipid mixtures were higher than those of either pure component. Therefore, the mixture of these surfactants accelerated the adsorption process and lowered the adsorption energy barrier, and the mixing of cationic and anionic surfactants was beneficial for dynamic surface activity. In conclusion, the cationic/anionic surfactant mixtures demonstrated good potential for the remediation of polycyclic aromatic hydrocarbon-contaminated soils from equilibrium and dynamic viewpoints.

Estimating Calibration Variability in Evapotranspiration Derived from a Satellite-Based Energy Balance Model

Computing evapotranspiration (ET) with satellite-based energy balance models such as METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) requires internal calibration of sensible heat flux using anchor pixels (“hot” and “cold” pixels). Despite the development of automated anchor pixel selection methods that classify a pool of candidate pixels using the amount of vegetation (normalized difference vegetation index, NDVI) and surface temperature (Ts), final pixel selection still relies heavily on operator experience. Yet, differences in final ET estimates resulting from subjectivity in selecting the final “hot” and “cold” pixel pair (from within the candidate pixel pool) have not yet been investigated. This is likely because surface properties of these candidate pixels, as quantified by NDVI and surface temperature, are generally assumed to have low variability that can be attributed to random noise. In this study, we test the assumption of low variability by first applying an automated calibration pixel selection process to 42 nearly cloud-free Landsat images of the San Joaquin area in California taken between 2013 and 2015. We then compute Ts (vertical near-surface temperature differences) vs. Ts relationships at all pixels that could potentially be used for model calibration in order to explore ET variance between the results from multiple calibration schemes where NDVI and Ts variability is intrinsically negligible. Our results show significant variability in ET (ranging from 5% to 20%) and a high—and statistically consistent—variability in dT values, indicating that there are additional surface properties affecting the calibration process not captured when using only NDVI and Ts. Our findings further highlight the potential for calibration improvements by showing that the dT vs. Ts calibration relationship between the cold anchor pixel (with lowest dT) and the hot anchor pixel (with highest dT) consistently provides the best daily ET estimates. This approach of quantifying ET variability based on candidate pixel selection and the accompanying results illustrate an approach to quantify the biases inadvertently introduced by user subjectivity and can be used to inform improvements on model usability and performance.

The evaluation of prostate lesions with IVIM DWI and MR perfusion parameters at 3T MRI.

The purpose of our study was to analyze the difference between IVIM DWI and perfusion parameters of malignant lesions and benign lesions-normal prostate tissue. This prospective study included 31 patients who had multiparametric prostate MRI with IVIM DWI due to elevated prostate-specific antigen level and clinical suspicion between February 2015 and September 2016. For peripheral zone, the mean values of Ktrans, Kep, iAUC, χ2 and f were significantly higher in malignant lesions, and the mean values of Dt were significantly lower in malignant lesions (p 0.00, p 0.02, p 0.00, p 0.02 and p 0.00, respectively). For transitional zone, the mean values of Ktrans, Ve, iAUC, χ2 and f were significantly higher in malignant lesions, and the mean values of Dp and Dt were significantly lower in malignant lesions (p 0.00, p 0.00, p 0.00, p 0.00, p 0.00, p 0.02 and p 0.00, respectively). For whole prostate gland, the mean values of Ktrans, Kep, Ve, iAUC, χ2 and f were significantly higher in malignant lesions, and the mean values of Dp and Dt were significantly lower in malignant lesions (p 0.00, p 0.03, p 0.00, p 0.00, p 0.00, p 0.01, p 0.04 and p 0.00, respectively). Restricted diffusion-pseudodiffusion and increased perfusion parameters are important to differentiate prostate cancer from benign pathologies. It is also important to keep in mind that transitional zone and peripheral zone tumors may have different perfusion and diffusion parameters. Future studies are needed to confirm our findings.

Preliminary Study of Computational Time Steps in a Physically Based Distributed Rainfall–Runoff Model

The choice of the computational time step (dt) value and the method for setting dt can have a bearing on the accuracy and performance of a simulation, and this effect has not been comprehensively researched across different simulation conditions. In this study, the effects of the fixed time step (FTS) method and the automatic time step (ATS) method on the simulated runoff of a distributed rainfall–runoff model were compared. The results revealed that the ATS method had less peak flow variability than the FTS method for the virtual catchment. In the FTS method, the difference in time step had more impact on the runoff simulation results than the other factors such as differences in the amount of rainfall, the density of the stream network, or the spatial resolution of the input data. Different optimal parameter values according to the computational time step were found when FTS and ATS were used in a real catchment, and the changes in the optimal parameter values were smaller in ATS than in FTS. The results of our analyses can help to yield reliable runoff simulation results.

Volumetric, Viscosity and Conductance Studies of Solute–Solute and Solute–Solvent Interactions of Some Alkali Metal Chlorides in Aqueous Citric Acid at Different Temperatures

Abstract The present study aims for the structure-making and structure-breaking behavior of some electrolytes in aqueous citric acid solution. The density, viscosity and conductance of some alkali metal chlorides lithium chloride (LiCl), sodium chloride (NaCl) and potassium chloride (KCl) in 0.01 m aqueous citric acid have been measured in the concentration range 0.01–0.12 m at 303.15, 308.15, 313.15 and 318.15 K. From these measurements, molar volume, viscosity parameters and molar conductance have been deliberated. Debye Hückel limiting law is used for the assessment of the contributions of various types of solute–solvent interactions. Jones–Dole viscosity equation is used to calculate viscosity B-coefficient for these salts in aqueous citric acid, which is known to provide information concerning the solvation of ions and their effects on the structure of the solvent in the near environment of the solute particles. The free energies of activation of viscous flow per mole of solvent, Δ μ 1 0 ‡ $\Delta \mu _1^{0\ddagger }$ and solute, Δ μ 2 0 ‡ , $\Delta \mu _2^{0\ddagger },$ have also been evaluated by using viscosity data. Using molar volume, the transfer volume Фv o tr has also been computed. The structure making/ breaking behavior of LiCl, NaCl and KCl is inferred from the sign of second derivative of partial molar volume with respect to temperature at constant pressure (d2φv o/dT2)p, Temperature coefficient of B. dB/dT and temperature coefficient of Walden product i.e. d(Λm oηo)/dT values. It has been found from these studies that LiCl, NaCl and KCl behave as structure-breaker in 0.01 m aqueous citric acid solution. The results have been qualitatively used to explain the molecular interaction and structural changes between the components of these mixtures.

Assessment of different mathematical models for diffusion-weighted imaging as quantitative biomarkers for differentiating benign from malignant solid hepatic lesions.

To quantitatively compare the monoexponential, biexponential, and stretched‐exponential diffusion‐weighted imaging (DWI) models in differentiating benign from malignant solid hepatic lesions. The institutional review board approved this retrospective study and waived the informed consent requirement. A total of 188 patients with 288 hepatic lesions included 202 malignant lesions and 86 benign lesions were assessed (confirmed by pathology or clinical follow‐up for 6 months). All patients underwent hepatic 3.0‐T MRI, including multi‐b DWI that used 12 b values. The ADC, D p, D t, perfusion fraction (f p), α, and DDC values for normal liver, benign liver lesions, and malignant liver lesions were calculated. Independent sample t tests were used for comparisons. The diagnostic performance of the parameters was evaluated using ROC analysis. The AUC value for each model was also calculated. The value of D p was significantly lower in benign lesions than in normal hepatic parenchyma while others were significantly higher (P < .001). Whereas Values of D t and α in malignant hepatic lesions were significantly higher than in normal hepatic parenchyma (P < .001), and the D p value was significantly lower (P < .001). Values of ADC, f p, DDC, and α for malignant hepatic lesions were significantly lower than those for benign hepatic lesions (P < .001). ROC analysis showed that the diagnostic value of the biexponential model of normal hepatic parenchyma vs benign hepatic lesions and normal hepatic parenchyma vs malignant hepatic lesions was high (0.946 and 0.876, respectively). In the differential diagnosis of benign and malignant hepatic lesions, DDC had the highest AUC value (0.819). The biexponential and stretched‐exponential DWI may provide additional information and improve the differential diagnosis of benign and malignant hepatic lesions compared with the monoexponential DWI.

Individual and combined efficacies of mild heat and ultraviolet-c radiation against Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in coconut liquid endosperm

This study determined the inactivation kinetic parameters of selected pathogens in heat, ultraviolet-C and combined heat-UV-C treated coconut liquid endosperm. Separate cocktails of Escherichia coli O157:H7, Salmonella enterica serovars, and Listeria monocytogenes strains were inoculated into coconut liquid endosperm (pH 5.15, TSS 4.4oBx, TA 0.062% malic acid, extinction coefficient (ε) at 254 nm of 0.0154 cm−1) for inactivation studies. Result showed that all organisms generally exhibited a log-linear heat inactivation behavior (R2 0.81–0.99). The E. coli O157:H7 cocktail (D55 = 19.75 min, D57 = 10.79 min, D60 = 3.38 min, and D63 = 0.46 min) was found to be significantly more resistant (P > 0.05) than the tested cocktail of L. monocytogenes (D55 = 11.68 min, D57 = 4.53 min, D60 = 1.82 min and D63 = 0.26 min) and S. enterica cocktail (D55 = 3.08 min, D57 = 2.60 min, D60 = 0.89 min and D63 = 0.25 min). Despite the differences in DT values, computed z values for L. monocytogenes cocktail (5.12 ± 0.43 °C) and E. coli O157:H7 cocktail (4.95 ± 0.12 °C) were not significantly different (P > 0.05), but were both significantly (P < 0.05) lower than that of S. enterica cocktail (7.10 ± 0.15 °C). All test organisms also exhibited a generally log-linear UV-C inactivation behavior (R2 0.90–0.99) with E. coli O157:H7 cocktail (DUV-C = 25.26 mJ/cm2) demonstrating greatest resistance to UV-C than S. enterica (DUV-C = 24.65 mJ/cm2) and L. monocytogenes (DUV-C = 17.30 mJ/cm2) cocktails. The D55 values of each organism cocktail were used to calculate for the 3-log reduction heating process schedules, during which UV-C treatments were simultaneously applied. Lethal rates (F values) calculations in the combined processes revealed that within the 3-log reduction heating processes, co-exposure of UV-C resulted in 5.62 to 6.20 log reductions in the test organism populations. Heating caused 69.3, 97.2, and 67.4% of the reduction in E. coli O157:H7, S. enterica and L. monocytogenes cocktails, respectively. These results can be used as baseline data in the establishment of mild heat treatment in combination with UV-C process schedules for coconut liquid endosperm and other similar products.

Experimental and theoretical investigations on the EPR parameters and molecular orbital bonding coefficients of VO2+ ions in BTTB glasses

The effect of the spin probe VO2+ in 15BaO–15TeO2–10TiO2-(60-x) B2O3–xV2O5 (x = 0.2, 0.4, 0.6, 0.8 mol %) glasses has been studied by employing Electron Paramagnetic Resonance (EPR) and optical absorption spectroscopic techniques. The observed EPR spectra of VO2+ ions were attributed on the basis of well-known spin-Hamiltonian of C4V symmetry. The simulated EPR spectra for VO2+ ions in the present glass system were drawn using Easy spin software. Both the experimental and simulated spectra were found to be in good agreement with each other. The optical absorption spectra exhibited three d–d transition bands due to crystal and tetragonal fields of VO2+ ions. These bands were assigned to 2B2g→ 2Eg, 2B2g→ 2B1g and 2B2g→ 2A1g transitions. The crystal field parameters Dq, Ds and Dt values are calculated. From the EPR and optical data, the molecular bonding coefficients were evaluated. Employing the higher order perturbation formulae of the g factors for 3d1 ion under tetragonally compressed octahedral fields, theoretical studies were carried out. The spin-Hamiltonian parameters and obtained from both the experimental and theoretical methods were in good agreement with each other.

Intravoxel Incoherent Motion Analysis of Abdominal Organs: Application of Simultaneous Multislice Acquisition.

The aim of this study was to systematically evaluate the accuracy of quantitative intravoxel incoherent motion (IVIM) analysis of the upper abdomen applying simultaneous multislice (SMS) diffusion-weighted imaging (DWI) to reduce acquisition time. Diffusion-weighted imaging of parenchymal abdominal organs was performed in 8 healthy volunteers at 3 T using a standard DWI sequence (acceleration factor 1 [AF1]) and an SMS-accelerated echo planar imaging sequence with acceleration factors 2 and 3 (AF2/AF3). Intravoxel incoherent motion analysis was performed with a multistep algorithm for true diffusion coefficient (Dt), pseudodiffusion coefficient (D*), and fraction of perfusion (Fp) measured for the liver, kidney cortex and medulla, pancreas, spleen, and erector spinae muscle. Qualitative and quantitative parameters were compared using a repeated measurement 1-way analysis of variance test and the Bonferroni post hoc method. Simultaneous multislice DWI provided diagnostic image quality in all volunteers with a reduction of scan time of 50% for AF2 (67% for AF3) compared with the standard sequence. Decent IVIM analysis for Dt, D*, and Fp can be calculated on the images of both the SMS sequences AF2 and AF3 with typical organ characteristics of IVIM; however, systematical deviations from AF1 were observed: Dt values increased and Fp decreased significantly with higher acceleration factor for liver, kidney, pancreas, and muscle (P < 0.05). Fitting curves of higher acceleration factors tend to be more monoexponentially shaped. Simultaneous multislice acceleration provides considerable scan time reduction for upper abdomen DWI with equivalent quality of IVIM analysis compared with the standard nonaccelerated technique. Systematic discrepancies of the true Dt, D*, and Fp for SMS acquisitions need to be considered when comparing to standard DWI sequences.

A High-Switching-Frequency Flyback Converter in Resonant Mode

The demand of miniaturization of power systems has accelerated the research on high-switching-frequency power converters. A flyback converter in resonant mode that features low switching losses, less transformer losses, and low switching noise at high switching frequency is investigated in this paper as an alternative to a conventional quasi-resonant (QR) flyback topology to increase power density. In order to find a compromise between magnet size, electromagnetic interference (EMI), and efficiency, the concept utilizes the resonant behavior between transformer leakage inductance and snubber capacitor to achieve near-zero-voltage switching at both turn-on and turn-off of the primary switch, low core loss due to a continuous transformer magnetizing current, and reduced EMI due to low di / dt and dv / dt values. Meanwhile, the concept uses the regenerative snubber to recycle the transformer leakage energy with two snubber diodes and one snubber capacitor. The proposed concept has been validated on a 340-kHz 65-W prototype. Compared to the conventional QR flyback converter operating at the same switching frequency, the proposed concept has 2% efficiency improvement and better EMI performance.

The inactivation kinetics of polyphenol oxidase and peroxidase in bayberry juice during thermal and ultrasound treatments

Abstract Ultrasound is recognized as a non-conventional processing technology for food preservation and quality improvement. Effects of thermal and ultrasound treatment on the inactivation kinetics of polyphenol oxidase (PPO) and peroxidase (POD) in bayberry juice were studied. Whether cooling with ice bath during ultrasound treatment was conducted to separate effects of heat and cavitation effects. In all processes, the inactivation kinetics of PPO and POD followed a first-order model (R2 = 0.864–0.997).The DT value during thermal inactivation varied from 151.99 to 6.23 min for PPO and the corresponding ZT values and activation energy (Ea) were 13.16 °C and 166.77 kJ/mol, while those parameters of POD were 298.26–7.08 min, 14.25 °C and 153.49 kJ/mol, respectively. The ultrasound (US) inactivation rate constants (k) for PPO ranged from 0.0556 min− 1 to 0.8878 min− 1 with the corresponding D values of 41.44–2.59 min and ZUI values of 312.50 W/cm2. However, the k value of PPO during ultrasound with cooling (USC) decreased to 0.0412–0.3268 min− 1, while the D and ZUI values increased to 55.92–7.05 min and 432.90 W/cm2, indicating that the heat brought out during ultrasound treatment significantly enhanced the inactivation kinetics of PPO. The inactivation rates of POD by US treatment were also higher than those by USC at the same ultrasound intensity and time. In addition, the kinetic parameters for POD by US and USC treatment were lower than those of PPO, inferring its more sonication resistant. Industrial relevance Ultrasound is a non-thermal food processing method for microorganism and enzyme inactivation, as well as quality maintenance. Attractive color is one of the most important quality attribute of bayberry products and strongly affects the consumer acceptance and preference. A key role in color degradation in berry fruit products is attributed to enzymatic browning of phenolic compounds which mainly related to PPO and POD. Therefore, the inactivation of PPO and POD is necessary for better color retention and shelf life increasing. This study would provide technical support for PPO and POD inactivation of ultrasound technique in bayberry juices processing.

Influence of simulated pulpal pressure on the variation of intrapulpal temperature during adhesive system light-curing

Objective: To evaluate the effects of simulated pulpal pressure (SPP) on the variation of intrapulpal temperature (DT) during light-curing of the adhesive system. Material e methods: One hundred sound human molars were sectioned from the highest pulp horn to obtain a 2-mm of thickness dentin. The specimens were randomly divided into two groups: (n=50), according to the presence or absence of SPP (15 cm H2O). The specimens were sequentially treated as follows: 37% phosphoric acid (Scotchbond Universal; 3M/ESPE), adhesive system (Scotchbond Universal/3M ESPE) and light-curing (10 seconds). DT was evaluated during adhesive light-curing with a K-type thermometer put inside the pulp chamber. Data were analysed by using Mann-Whitney’s test (at 5%). Results: According to Mann-Whitney’s test, the absence group presented a DT of 2°C, whereas the presence group 1°C. The mean values of DT were 0.82±0.56°C for the presence group and 2.30±0.73°C for the absence group. Conclusions: Simulated pulpal pressure significantly reduced the temperature rise in the pulp chamber during light-curing of the adhesive system, showing the importance of inserting this protocol of simulated pulpal pressure in the laboratory procedures. Keywords: Dentin; Light-curing; Pulpal pressure; Temperature.

Variation of Threshold Voltage With Temperature in Impact Ionization-Induced Steep Switching Si and Ge Junctionless MOSFETs

In this paper, we report on the anomalous behavior of threshold voltage ( ${V} _{\sf th})$ with temperature in junctionless (JL) transistors. It is shown that both positive and negative values of temperature coefficient of threshold voltage ( dV $_{\sf th}$ / dT ) in nMOS Si and Ge JL devices can occur at higher drain biases. At lower temperatures, ${V} _{\sf th}$ reduces with a decrease in temperature due to the dominance of bipolar effects over thermal generation of carriers, whereas at higher temperatures, thermal generation results in essentially unipolar characteristics, and ${V} _{\sf th}$ reduces with increase in temperature. It is also shown that zero temperature coefficient condition shall be nonexistent under dominant bipolar conduction over unipolar operation. Results show new viewpoints to understand the two contrasting physical mechanisms leading to positive and negative dV $_{\sf th}$ / dT values in JL devices.

Turbulent eddy diffusion models in exposure assessment - Determination of the eddy diffusion coefficient

ABSTRACTThe use of the turbulent eddy diffusion model and its variants in exposure assessment is limited due to the lack of knowledge regarding the isotropic eddy diffusion coefficient, DT. But some studies have suggested a possible relationship between DT and the air changes per hour (ACH) through a room. The main goal of this study was to accurately estimate DT for a range of ACH values by minimizing the difference between the concentrations measured and predicted by eddy diffusion model. We constructed an experimental chamber with a spatial concentration gradient away from the contaminant source, and conducted 27 3-hr long experiments using toluene and acetone under different air flow conditions (0.43–2.89 ACHs). An eddy diffusion model accounting for chamber boundary, general ventilation, and advection was developed. A mathematical expression for the slope based on the geometrical parameters of the ventilation system was also derived. There is a strong linear relationship between DT and ACH, providing a surrogate parameter for estimating DT in real-life settings. For the first time, a mathematical expression for the relationship between DT and ACH has been derived that also corrects for non-ideal conditions, and the calculated value of the slope between these two parameters is very close to the experimentally determined value. The values of DT obtained from the experiments are generally consistent with values reported in the literature. They are also independent of averaging time of measurements, allowing for comparison of values obtained from different measurement settings. These findings make the use of turbulent eddy diffusion models for exposure assessment in workplace/indoor environments more practical.

A Theoretical Analysis for Assessing the Variability of Secondary Model Thermal Inactivation Kinetic Parameters.

Traditionally, for the determination of the kinetic parameters of thermal inactivation of a heat labile substance, an appropriate index is selected and its change is measured over time at a series of constant temperatures. The rate of this change is described through an appropriate primary model and a secondary model is applied to assess the impact of temperature. By this approach, the confidence intervals of the estimates of the rate constants are not taken into account. Consequently, the calculated variability of the secondary model parameters can be significantly lower than the actual variability. The aim of this study was to demonstrate the influence of the variability of the primary model parameters in establishing the confidence intervals of the secondary model parameters. Using a Monte Carlo technique and assuming normally distributed DT values (parameter associated with a primary inactivation model), the error propagating on the DTref and z-values (secondary model parameters) was assessed. When DT confidence intervals were broad, the secondary model’s parameter variability was appreciably high and could not be adequately estimated through the traditional deterministic approach that does not take into account the variation on the DT values. In such cases, the proposed methodology was essential for realistic estimations.

Intravoxel incoherent motion (IVIM) histogram biomarkers for prediction of neoadjuvant treatment response in breast cancer patients

ObjectiveTo examine the prognostic capabilities of intravoxel incoherent motion (IVIM) metrics and their ability to predict response to neoadjuvant treatment (NAT). Additionally, to observe changes in IVIM metrics between pre- and post-treatment MRI. MethodsThis IRB-approved, HIPAA-compliant retrospective study observed 31 breast cancer patients (32 lesions). Patients underwent standard bilateral breast MRI along with diffusion-weighted imaging before and after NAT. Six patients underwent an additional IVIM-MRI scan 12–14 weeks after initial scan and 2 cycles of treatment. In addition to apparent diffusion coefficients (ADC) from monoexponential decay, IVIM mean values (tissue diffusivity Dt, perfusion fraction fp, and pseudodiffusivity Dp) and histogram metrics were derived using a biexponential model. An additional filter identified voxels of highly vascular tumor tissue (VTT), excluding necrotic or normal tissue. Clinical data include histology of biopsy and clinical response to treatment through RECIST assessment. Comparisons of treatment response were made using Wilcoxon rank-sum tests. ResultsAverage, kurtosis, and skewness of pseudodiffusion Dp significantly differentiated RECIST responders from nonresponders. ADC and Dt values generally increased (∼70%) and VTT% values generally decreased (∼20%) post-treatment. ConclusionDp metrics showed prognostic capabilities; slow and heterogeneous pseudodiffusion offer poor prognosis. Baseline ADC/Dt parameters were not significant predictors of response. This work suggests that IVIM mean values and heterogeneity metrics may have prognostic value in the setting of breast cancer NAT.