Double Exponential Fit Research Articles

Linking Metastatic Potential and Viscoelastic Properties of Breast Cancer Spheroids via Dynamic Compression and Relaxation in Microfluidics.

The growth and invasion of solid tumors are associated with changes in their viscoelastic properties, influenced by both internal cellular factors and physical forces in the tumor microenvironment. Due to the lack of a comprehensive investigation of tumor tissue viscoelasticity, the relationship between such physical properties and cancer malignancy remains poorly understood. Here, the viscoelastic properties of breast cancer spheroids, 3D (in vitro) tumor models, are studied in relation to their metastatic potentials by imposing controlled, dynamic compression within a microfluidic constriction, and subsequently monitoring the relaxation of the imposed deformation. By adopting a modified Maxwell model to extract viscoelastic properties from the compression data, the benign (MCF-10A) spheroids are found to have higher bulk elastic modulus and viscosity compared to malignant spheroids (MCF-7 and MDA-MB-231). The relaxation is characterized by two timescales, captured by a double exponential fitting function, which reveals a similar fast rebound for MCF-7 and MCF-10A. Both the malignant spheroids exhibit similar long-term relaxation and display residual deformation. However, they differ significantly in morphology, particularly in intercellular movements. These differences between malignant spheroids are demonstrated to be linked to their cytoskeletal organization, by microscopic imaging of F-actin within the spheroids, together with cell-cell adhesion strength.

Ni2+ concentration-dependent and temperature-dependent NIR photoluminescence properties in novel transparent glass-ceramics containing cubic CaTa2O6: Ni2+ nanocrystals

Novel transparent glass-ceramics (TGCs) containing cubic α-CaTa2O6: Ni2+ nanocrystals and their Ni2+ concentration-dependent and temperature-dependent spectroscopic properties were reported. They were obtained from precursor glasses (PGs) with a subsequent heat treatment, in which the PGs of 31CaO-31Ta2O5-38Al2O3-xNiO (x = 0.02–1.5 in mol%) were prepared by the aerodynamic levitation technique. A broadband near-infrared (NIR) emission with a full width at half maximum (FWHM) of ∼250 nm was observed at ∼1220 nm under excitation at 980 nm, attributing to the spin-allowed transition of 3T2g (3F) → 3A2g (3F) of Ni2+ in octahedral Ta5+ sites in α-CaTa2O6. With the increasing of NiO content, the emission intensity increases at first reaching a maximum at x = 0.3 mol%, and then declines. A red-shifting emission from 1189 to 1258 nm is observed with a broadening FWHM from 218 to 292 nm and a significantly reducing average lifetime from 594.4 to 56.0 μs. When the temperature increased from 298 to 473 K, the emission shows an apparent thermal quenching with a blue shift of 15 nm, where the intensity remained 51 % at 373 K of that at 298 K. Furthermore, it supposes that there are two types of Ni2+ active centers according to the deconvolution of the photoluminescence (PL) spectra, double-exponential fitting of the decay curves and temperature-dependent PL spectra. One shows a stronger concentration quenching, while the other exhibits a more serious thermal quenching. The possible thermal quenching mechanism was also discussed.

Positronium lifetime validation measurements using a long-axial field-of-view positron emission tomography scanner

BackgroundPositron emission tomography (PET) traditionally uses coincident annihilation photons emitted from a positron interacting with an electron to localize cancer within the body. The formation of positronium (Ps), a bonded electron-positron pair, has not been utilized in clinical applications of PET due to the need to detect either the emission of a prompt gamma ray or the decay of higher-order coincident events. Assessment of the lifetime of the formed Ps, however, can potentially yield additional diagnostic information of the surrounding tissue because Ps properties vary due to void size and molecular composition. To assess the feasibility of measuring Ps lifetimes with a PET scanner, experiments were performed in a Biograph Vision Quadra (Siemens Healthineers). Quadra is a long-axial field-of-view (LA-FOV) PET scanner capable of producing list-mode data from single interaction events.ResultsOrtho-Ps (o-Ps) lifetimes were measured for quartz-glass and polycarbonate samples using a 22Na\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{22}\ ext{Na}$$\\end{document} positron source. Results produced o-Ps lifetimes of 1.538 ± 0.036 ns for the quartz glass and 1.927 ± 0.042 ns for the polycarbonate. Both o-Ps lifetimes were determined using a double-exponential fit to the time-difference distribution between the emission of a prompt gamma ray and the annihilation of the correlated positron. The measured values match within a single standard deviation of previously published results. The quartz-glass samples were additional measured with 82Rb\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${^{82}}\ ext{Rb}$$\\end{document}, 68\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{68}$$\\end{document}Ga and 124I\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{124}\ ext{I}$$\\end{document} to validate the lifetime using clinically available sources. A double-exponential fit was initially chosen as a similar methodology to previously published works, however, an exponentially-modified Gaussian distribution fit to each lifetime more-accurately models the data. A Bayesian method was used to estimate the variables of the fit and o-Ps lifetime results are reported using this methodology for the three clinical isotopes: 1.59 ± 0.03 ns for 82Rb\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{82}\ ext{Rb}$$\\end{document}, 1.58 ± 0.07 ns for 68Ga\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{68}\ ext{Ga}$$\\end{document} and 1.62 ± 0.01 ns for 124I\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{124}\ ext{I}$$\\end{document}. The impact of scatter and attenuation on the o-Ps lifetime was also assessed by analyzing a water-filled uniform cylinder (20 ϕ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\phi$$\\end{document}×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 30 cm3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{3}$$\\end{document}) with an added 82Rb\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{82}\ ext{Rb}$$\\end{document} solution. Lifetimes were extracted for various regions of the cylinder and while there is a shape difference in the lifetime due to scatter, the extracted o-Ps lifetime of the water, 1.815 ± 0.013 ns, agrees with previously published results.ConclusionOverall, the methodology presented in this manuscript demonstrates the repeatability of Ps lifetime measurements with clinically available isotopes in a commercially-available LA-FOV PET scanner. This validation work lays the foundation for future in-vivo patient scans with Quadra.

Na-doped Li4SiO4 as an efficient sorbent for low-concentration CO2 capture at high temperature: Superior adsorption and rapid kinetics mechanism

Lithium silicate (Li4SiO4) sorbent has garnered attention in CO2 capture due to its high theoretical adsorption capacity and fast kinetics. However, its adsorption capacity and kinetics were hindered by low CO2 concentration. Improving adsorption performance of Li4SiO4 at low CO2 concentration has become the key to industrial application. In this work, high-activity Na-doped Li4SiO4 with controllable active substance Li3NaSiO4 was achieved. The influences of raw materials ratios on the CO2 adsorption performance were systematically investigated. When RLi/Si=4.05:1 and RNa/Si=0.15:1, the sample exhibited the highest adsorption capacity of 32.28 wt% with an equilibrium time of 29 min, and a superior stable capacity of 31.09 wt% in 15 cycles. Importantly, the double exponential fitting revealed that LiNaCO3 accelerated the ion diffusion rate and real-time adsorption processes showed Li3NaSiO4 expedited surface chemical reaction rate. Based on these, a novel Na2CO3 eutectic doping mechanism was proposed. The active substance Li3NaSiO4, generated through Na doping, along with its product formed from the reaction with CO2, molten LiNaCO3, acted synergistically to improve adsorption performance by accelerating surface chemical reaction rate and ion diffusion rate. Compared with other doped Li4SiO4, the sorbent prepared in this work demonstrated competitive adsorption performance, providing theoretical and technical support for the large-scale production of high-activity Li4SiO4.

Do attenuation coefficients based on luminescence bleaching fronts reflect true light attenuation in rocks?

The emerging technique of rock surface luminescence dating employs a double-exponential fitting dating model based on the Bouguer-Lambert law. The accuracy of exposure age determination is sensitive to the light attenuation coefficient, μ, which is usually derived from fitting the luminescence profile as a function of depth into the rock. Alternatively, μ might be determined by direct measurement using a spectrophotometer. However, their directly measured values of μ were significantly larger than those estimated from field luminescence bleaching data. Here, we aim to confirm these previous results by measuring the luminescence-depth profiles of both IRSL and IRPL signals from granite rock exposed to different light sources, including sunlight, SOL2 and IR LEDs under controlled conditions. We also measured monochromatic light (blue LED: (470 ± 30) nm, green LED: (520 ± 30) nm, and infrared LED: (850 ± 30) nm) attenuation in granite rock slices of varying thickness (0.62–2.60 mm) using a high-sensitivity photodiode. Finally, we use a camera-based measurement system and a Risø Luminescence Imager to investigate spatial variation in transmitted light as a function of slice thickness. The spatial correlation between direct light transmission and luminescence emission is then investigated, to investigate the underlying reasons for the difference between direct measurement and luminescence-based estimates of μ. We find that light attenuation through a granite rock slice is very heterogeneous; most light penetrates through localized low attenuation light paths corresponding to transmission through the most transparent grains, presumably quartz. The light penetration and escape into the surrounding matrix are assumed to be influenced by the surface area of quartz grains. As a result, transmissive light paths result in a significant area of feldspar grains at depth in the slice being exposed to more light than might be expected from average attenuation measurement. When the incident light predominantly travels through feldspar minerals, simultaneously stimulating luminescence from within any potassium feldspar (K-feldspar), the attenuation coefficients derived from the luminescence-depth profiles tend to be smaller than the average of 1.18 ± 0.07 (n = 79) irrespective of the kinetic model used for fitting. Thus, luminescence-based attenuation coefficient estimates appear to be affected by the distribution of light attenuation across and within the rock slice, making such estimates preferable to directly measured (average) estimates of light attenuation coefficients. These insights are important for our understanding of the significance of light attenuation coefficients in rock samples; they contribute to the reassessment of parameters and measurement methods in dating models and so to improvements in accuracy of rock surface luminescence dating techniques.

Fluorescence Lifetime Imaging of Human Retinal Pigment Epithelium in Pentosan Polysulfate Toxicity Using Adaptive Optics Scanning Light Ophthalmoscopy.

Fluorescence lifetime ophthalmoscopy (FLIO) is an emerging clinical modality that could provide biomarkers of retinal health beyond fluorescence intensity. Adaptive optics (AO) ophthalmoscopy provides the confocality to measure fluorescence lifetime (FL) primarily from the retinal pigment epithelium (RPE) whereas clinical FLIO has greater influence from fluorophores in the inner retina and lens. Adaptive optics fluorescence lifetime ophthalmoscopy (AOFLIO) measures of FL in vivo could provide insight into RPE health at different stages of disease. In this study, we assess changes in pentosan polysulfate sodium (PPS) toxicity, a recently described toxicity that has clinical findings similar to advanced age-related macular degeneration. AOFLIO was performed on three subjects with PPS toxicity (57-67years old) and six age-matched controls (50-64years old). FL was analyzed with a double exponential decay curve fit and with phasor analysis. Regions of interest (ROIs) were subcategorized based on retinal features on optical coherence tomography (OCT) and compared to age-matched controls. Twelve ROIs from PPS toxicity subjects met the threshold for analysis by curve fitting and 15 ROIs met the threshold for phasor analysis. Subjects with PPS toxicity had prolonged FL compared to age-matched controls. ROIs of RPE degeneration had the longest FLs, with individual pixels extending longer than 900 ps. Our study shows evidence that AOFLIO can provide meaningful information in outer retinal disease beyond what is obtainable from fluorescence intensity alone. More studies are needed to determine the prognostic value of AOFLIO.

Chemical Recalcitrance Rather Than Soil Microbial Community Determined Short-Term Biochar Stability in a Poplar Plantation Soil

The stability of biochar is fundamental to its soil carbon (C) sequestration potential. The relative importance of chemical recalcitrance and the soil microbial community on biochar stability is still unclear. To unveil the question, we conducted a 60-day incubation to explore the stability of two rice-straw-derived biochars pyrolyzed at 300 and 500 °C (denoted as BS300 and BS500), as well as the relative contribution of the soil microbial community and biochar chemical recalcitrance to biochar stability in a poplar plantation soil. Biochar-derived cumulative carbon dioxide (CO2) emission was estimated to be 41.3 and 6.80 mg C kg−1, accounting for 0.73 and 0.11% of the amended biochar-derived organic C (OC) in BS300 and BS500 treatments, respectively. The mean retention time (MRT) estimated by double-exponential model fitting was 49.4 years for BS300 and 231 years for BS500. Compared to control, BS300 and BS500 decreased β-D-glucosidase activity by 20.9 and 18.0%, while they decreased phenol oxidase activity by 31.8 and 18.9%, respectively. Furthermore, BS300 increased the soil microbial metabolic quotient (qCO2) by 155%, but BS500 decreased it by 13.4%. In addition, BS300 resulted in a 520% higher biochar-derived hot-water-extractable OC than BS500. Partial least-squares path modeling (PLSPM) showed that the path efficients of biochar’s chemical recalcitrance and microbial qCO2 were 0.52 and 0.25, respectively, and that of the soil microbial activity is neglected. We conclude from this short-term study that chemical recalcitrance imposed a greater effect than soil microbial community on biochar stability.

A green light emissive LaSr2AlO5:Er3+ nanocrystalline material for solid state lighting: crystal phase refinement and down-conversion photoluminescence with high thermal stability.

The present study reveals the structural and optoelectronic characteristics of a down-converted (DC) green luminous Er3+ doped LaSr2AlO5 phosphor that was produced by employing an efficient and reliable gel-combustion process assisted with urea as a fuel. Using Rietveld refinement of diffraction data, the crystal structure and phase formation were examined. The surface morphology and elemental configuration of the phosphor were analyzed via TEM and EDX spectroscopy, respectively. The band gap of LaSr2AlO5 (5.97 eV) and optimized La0.96Sr2AlO5:4 mol% Er3+ (5.51 eV) classify the optimized sample as a direct band-gap material. The PL peaks located in the visible range corresponding to transitions 2H9/2 → 4I15/2 (406 nm), 2H11/2 → 4I15/2 (520 nm), 4S3/2 → 4I15/2 (550 nm), and 4F9/ 2 → 4I15/2 (665 nm) were revealed by photoluminescence spectroscopy under 377 nm excitation. Above 4 mol% Er3+ doping, concentration quenching was observed, which was controlled by the quadrupole-quadrupole interaction. Based on the findings of the double exponential fitting of lifetime curves acquired from the emission spectra at λex = 377 nm and λem = 550 nm, the average lifetime of the excited levels of considered nanomaterials was estimated. The temperature-dependent emission spectra of the La0.96Sr2AlO5:4 mol% Er3+ sample were collected in the range 298-498 K. The considered phosphor was found to have a high thermal stability as evidenced by the luminous intensity being sustained at 74.29% at 498 K compared to the intensity at ambient temperature (298 K) with an activation energy of 0.1453 eV. The calculated color purity and superb chromaticity coordinates indicates that the phosphors have a high degree of color purity, which further supports its applicability as a green component in solid-state lighting.

Experimental and Theoretical Study of the Kinetics of the CH3 + HBr → CH4 + Br Reaction and the Temperature Dependence of the Activation Energy of CH4 + Br → CH3 + HBr.

The rate coefficient of the reaction of CH3 with HBr was measured and calculated in the temperature range 225-960 K. The results of the measurements performed in a flow apparatus with mass spectrometric detection agree very well with the quasiclassical trajectory calculations performed on a previously developed potential energy surface. The experimental rate coefficients are described well with a double-exponential fit, k1(exp) = [1.44 × 10-12 exp(219/T) + 6.18 × 10-11 exp(-3730/T)] cm3 molecule-1 s-1. The individual rate coefficients below 500 K accord with the available experimental data as does the slightly negative activation energy in this temperature range, -1.82 kJ/mol. At higher temperatures, the activation energy was found to switch sign and it rises up to about an order of magnitude larger positive value than that below 500 K, and the rate coefficient is about 50% larger at 960 K than that around room temperature. The rate coefficients calculated with the quasiclassical trajectory method display the same tendencies and are within about 8% of the experimental data between 960 and 300 K and within 25% below that temperature. The significant variation of the magnitude of the activation energy can be reconciled with the tabulated heats of formation only if the activation energy of the reverse CH4 + Br reaction also significantly increases with the temperature.

Exponential modelling of heart rate recovery after a maximal exercise

Objectives: Heart rate recovery (HRR) after exercise is clinically important as a predictor of mortality. In addition, HRR is an indicator of cardiac autonomic activity, since increased vagal activity and diminished sympathetic activity return the heart rate to resting conditions after exercise. The previous attempts to model HRR using polynomial, first-order and second-order modelling have produced mixed results. In this study, we hypothesised that the double-exponential fit would model the HRR more accurately than the single-exponential fit as it would capture the activity of both autonomic arms responsible for heart rate decay and investigated the outcome of these two models on the HRR data following a maximal exercise. Materials and Methods: Exponential curve fitting was done on a set of previously published data from our laboratory. The HRR data were acquired from 40 male participants (19–38 years) after a maximal treadmill exercise. The normalised HRR data from a 5-min time window from maximal heart rate were fitted using single and double-exponential curves, to obtain, respectively, the time constants Tau and, Tau 1 and Tau 2. The goodness-of-fit of the model was assessed with Chi-square values computed for each participant data set with both models. Considering that Chi-square of zero is a perfect fit, and therefore, smaller Chi-square values indicate a better fit than larger values, we computed the difference in the Chi-square values (Δχ2) between the models by subtracting the Chi-square value of the double-exponential fit from the Chi-square value of the single-exponential fit. This was based on the premise that if the calculated Δχ2 is positive, it would indicate a better fit with double-exponential than single-exponential decay model. The data are presented as mean ± standard deviation. Comparisons were made with Student’s t-test. Results: Data from four participants were excluded for technical reasons. The Tau of the single-exponential fit was 65.50 ± 12.13 s, while Tau 1 and Tau 2 of the double-exponential fit were 43.75 ± 18.96 s and 120.30 ± 91.32 s, respectively, the Tau 1 value being significantly lower than the Tau 2 value (P < 0.0001). Remarkably among the 36 participants, the difference in the Chi-square value was positive (127.2 ± 171.04) in 22 subjects and zero or marginally negative (−0.17 ± 0.31) in 14 subjects. Conclusion: Our results indicate that the double-exponential model fitted the HRR data better than the single-exponential model in almost two-thirds (61%) of our study population. In the remaining participants, the goodness-of-fit was nearly equivalent for both fits with no evidence of superior modelling with the single-exponential fit. Our data show that while the single-exponential fit is sufficient for modelling the HRR of 14 subjects, it was less efficient for fitting the data of most participants. In comparison, the double-exponential curve fit effectively modelled 100% of our study population. Given our findings, we conclude that the double-exponential model is more inclusive and better represented the HRR data of our study population than the single-exponential model.

Photoinduced doping in hexagonal boron nitride

Hexagonal boron nitride is shown to exhibit very significant persistent photoconductivity after UV illumination. This behavior can be initiated by sub-bandgap or close to bandgap illumination. Neither temperature nor pressure affects the buildup of photoinduced carriers. The effect persists at least for months at room temperature and is maintained significantly after heating up to 300 °C. Up to six orders of magnitude increased conductivity has been durably established in the devices, and the effect is reproducible. Double exponential fitting gives time constants up to 4600 days. Irradiation after having saturated the devices is shown to drastically reduce the decay rate. The bulk origin of such effect has been demonstrated. p-hBN/n-AlGaN diodes based on magnesium doped h-BN have been used to determine the type of conductivity through studies of junction capacitance variations under UV irradiation. Depending on illumination wavelength, both n- and p-type durable photoinduced carriers can be produced. These results are of interest for UVC LEDs in which the usual conductive AlGaN layers are still a hurdle toward efficient UV emitters.

Photoluminescence and quantum yield behaviour of vanadium doped Zn2SiO4 phosphors facilely synthesized by sol-gel method

Vanadium-doped Zinc Silicate (Zn2SiO4) phosphors were synthesized through the sol-gel method. Structural, morphological and optical techniques were used to investigate the effects of vanadium incorporation on their structure, morphology, and optical behaviour. We reported that vanadium incorporation in Zn2SiO4 phosphors significantly modifies their crystallinity, morphology, and photoluminescence properties. When vanadium is added to Zn2SiO4 phosphors, the energy band gap (Eg) changes from 5.29 to 2.34 eV. Vanadium dopants generate imperfections in Zn2SiO4 phosphors, the leading cause of their emissions in visible regions and quantum yield. Quantum yield is estimated at 7.06% for Zn2−xVxSiO4 (x = 0.08) phosphor. The luminescence decay lifetime of the prominent emissions of vanadium-doped Zn2SiO4 was measured using a double exponential fitting technique, and the average lifetime is 11.7 ns.

A multi-color carbon quantum dots based on the coordinated effect of quantum size and surface defects with green synthesis

As an important complement to traditional quantum dots (QDs), carbon quantum dots (CQDs) possess the characteristics of low toxicity, easy preparation, low cost, and good biocompatibility. Here, we have successfully prepared blue, yellow-green, yellow and red emitting CQDs by a one-step solvothermal method using o-phenylenediamine as a precursor and only water and ethanol as solvents. It is noted that the diameter of CQDs satisfies the quantum size effect, which is also corroborated by the reduced graphitization. The decay processes of CQDs obey double exponential fit. The x-ray photoelectron spectroscopy (XPS) conclusively determines that the red-shift from yellow-green to red CQDs is associated with the carbon-/oxygen-related surface defects except for the quantum size effect. Intriguingly, multi-color CQDs-based LEDs devices using thermoset epoxy resins have been successfully fabricated, which illustrates the great potential of CQDs for future applications in the luminescence field due to their superior performance and environmentally friendly fabrication.

Mitochondrial Sensitivity To Submaximal ADP Concentrations Following Bed Rest: A Double Exponential Model Analysis

We recently demonstrated that a 10-day exposure to inactivity/microgravity (bed rest, BR) determined impairments of peak oxygen uptake (V̇O2), peak cardiac output, peripheral and microvascular function, whereas maximal ADP-stimulated mitochondrial respiration ex vivo in isolated permeabilized fibers and muscle V̇O2 off-kinetics in vivo were unaffected. PURPOSE: To evaluate mitochondrial sensitivity to submaximal [ADP]. METHODS: Isolated permeabilized vastus lateralis fibers were analyzed by high-resolution respirometry, before (PRE) and after (POST) a 10-day BR in 10 young males. 11 submaximal titrations of ADP (from 12.5 to 10,000 μM) were utilized to assess complex I + II-linked ADP sensitivity which was analyzed by both a Michaelis-Menten (MM) kinetics equation, with the calculation of the apparent Km by standard methods, and by applying a double-exponential function, with the calculation of [ADP] corresponding to 50% of the maximal mitochondrial respiration ([ADP] at 50% JO2max). RESULTS: The double-exponential function provided a better fitting of the data according to AIC model selection. The sum of squared residuals was substantially lower with the double-exponential vs. MM fitting (411 ± 419 and 1209 ± 495 [pmol/s/mg]2, respectively). R2 was higher with the double-exponential vs. the MM fitting (0.97 ± 0.04 and 0.90 ± 0.05, respectively). Analysis of residuals showed that the fitting by MM markedly overestimated JO2 from 1000 to 2000 μM, and underestimated JO2 from 6000 to 10,000 μM. The apparent Km for MM was lower than the [ADP] at 50% JO2max, both in PRE (843 ± 706 and 1270 ± 1015 μM, respectively) and in POST (375 ± 173 and 409 ± 398 μM, respectively). Only for the [ADP] at 50% JO2max the difference between POST vs. PRE was statistically significant (P = 0.046). CONCLUSIONS: The double-exponential function provided a better fit of experimental data. It might also give insights into cellular mechanisms regulating mitochondrial respiration, possibly related to the transport of nucleotides and phosphate across external and internal mitochondrial membranes, ATP synthase activity and respiratory chain activity. The enhanced mitochondrial sensitivity to submaximal [ADP] after BR could represent an attempt to maintain metabolic homeostasis in the presence of impairments upstream of mitochondria.

A Novel Adaptive Back Propagation Neural Network-Unscented Kalman Filtering Algorithm for Accurate Lithium-Ion Battery State of Charge Estimation

Accurate State of Charge (SOC) estimation for lithium-ion batteries has great significance with respect to the correct decision-making and safety control. In this research, an improved second-order-polarization equivalent circuit (SO-PEC) modelling method is proposed. In the process of estimating the SOC, a joint estimation algorithm, the Adaptive Back Propagation Neural Network and Unscented Kalman Filtering algorithm (ABP-UKF), is proposed. It combines the advantages of the robust learning rate in the Back Propagation (BP) neural network and the linearization error reduction in the Unscented Kalman Filtering (UKF) algorithm. In the BP neural network part, the self-adjustment of the learning factor accompanies the whole estimation process, and the improvement of the self-adjustment algorithm corrects the shortcomings of the UKF algorithm. In the verification part, the model is validated using a segmented double-exponential fit. Using the Ampere-hour integration method as the reference value, the estimation results of the UKF algorithm and the Back Propagation Neural Network and Unscented Kalman Filtering (BP-UKF) algorithm are compared, and the estimation accuracy of the proposed method is improved by 1.29% under the Hybrid Pulse Power Characterization (HPPC) working conditions, 1.28% under the Beijing Bus Dynamic Stress Test (BBDST) working conditions, and 2.24% under the Dynamic Stress Test (DST) working conditions. The proposed ABP-UKF algorithm has good results in estimating the SOC of lithium-ion batteries and will play an important role in the high-precision energy management process.

Understanding the Influence of Diverse Non-Volatile Media on Rheological Properties of Thermophilic Biological Sludge and Evaluation of Its Thixotropic Behaviour

In this study, the rheological properties of thermophilic biological sludge (TBS) have been investigated evaluating the influence of non-volatile solids (NVS). Calcium carbonate, sand, and sodium bentonite were separately added to the sludge to evaluate the effect of concentration and type of NVS. Results show that TBS consistency coefficient significantly enhanced increasing sodium bentonite concentration. On the contrary, calcium carbonate and sand showed relatively small influence on the rheological properties of TBS. Thixotropic behaviour of TBS has also been investigated and is more pronounced at higher shear rate (1000 s−1). Double exponential fitting model was the best choice to represent thixotropic behaviour in case of low (100 s−1) and high shear rate (1000 s−1), while a single-exponential model represents the best option in case of medium shear rate (400 s−1).

Estimation of Nuclear Medicine Exposure Measures Based on Intelligent Computer Processing.

This paper provides an in-depth discussion and analysis of the estimation of nuclear medicine exposure measurements using computerized intelligent processing. The focus is on the study of energy extraction algorithms to obtain a high energy resolution with the lowest possible ADC sampling rate and thus reduce the amount of data. This paper focuses on the direct pulse peak extraction algorithm, polynomial curve fitting algorithm, double exponential function curve fitting algorithm, and pulse area calculation algorithm. The detector output waveforms are obtained with an oscilloscope, and the analysis module is designed in MATLAB. Based on these algorithms, the data obtained from six different lower sampling rates are analyzed and compared with the results of the high sampling rate direct pulse peak extraction algorithm and the pulse area calculation algorithm, respectively. The correctness of the compartment model was checked, and the results were found to be realistic and reliable, which can be used for the analysis of internal exposure data in radiation occupational health management, estimation of internal exposure dose for nuclear emergency groups, and estimation of accidental internal exposure dose. The results of the compartment model of the respiratory tract and the compartment model of the digestive tract can be used to calculate the distribution and retention patterns of radionuclides and their compounds in the body, which can be used to assess the damage of radionuclide internal contamination and guide the implementation of medical treatment.

Nanosecond-order long–short fluorescence lifetime switchable encryption with enlarged coding capacity

Abstract The turn-off fluorescent photoswitches for information encryption are constantly being developed. However, there are no reports about time-switchable (fluorescence lifetime-switchable) encryption to overcome the limitations of tunable encoding numbers in spectrally and temporally encoded libraries. Based on the double-exponential fitting of fluorescence lifetime, we propose, a fatigue-free and highly flexible switch between the amplitude-weighted average fluorescence lifetime (τm) and the intensity-weighted average fluorescence lifetime (τi), which will realize the supermultiplexed fluorescence lifetime switchable encryption. The potentially enormous library of different fluorescent lifetime combinations would facilitate the development of information security.

Lifetime Division Multiplexing by Multilevel Encryption Algorithm.

Asymmetric, multilevel, switchable, and reversible encryption is realized by algorithm encryption, which plays an important role in encryption technology. Fluorescence lifetime encryption is currently not executed by an algorithm. It is well-known that the short fluorescence lifetime (τ1), long fluorescence lifetime (τ2), amplitude-weighted average fluorescence lifetime (τm), and intensity-weighted average fluorescence lifetime (τi) can be obtained using a double exponential fitting, and then these four lifetime parameters can be considered as four lifetime algorithms. Therefore, we propose that the acquisition of these four fluorescence lifetimes can be regarded as further dividing the lifetime by different algorithms and optimizing lifetime multiplexing. Moreover, the four lifetime algorithms of τ1, τm, τ2, and τi can be switched between each other and can be used to perform asymmetric, multilevel, and reversible lifetime encryption to effectively increase the difficulties of anticounterfeiting.

Traps energy distribution in Kapton HN polyimide films through surface potential decay model under humidity conditions

In this paper, an experimental study and analysis of the effects of environmental relative humidity (RH %) on the transport mechanisms of electrical charges in 50 μm thick Kapton HN polyimide (PI) films have been presented. The evolution of the surface potential decay with time after negative corona charge deposition have been investigated and analyzed by examining the tdV/dt characteristics to straightly obtain information about trap energy distribution in PI films for different relative humidity levels (35, 50, 70 and 90%). The calculating method of trap energy distribution is based on the double exponential fitting analysis of surface potential decay measurements. Two peaks were observed in the trap charge density distribution curve with trap levels, which is agreed with the presence of the shallow and deep traps. The results indicate that for different charging voltage levels, the surface potential decays faster in humid air (RH = 90%) than in relatively dry ones (RH = 35%). The recorded corona charging current confirms the interpretation of surface potential decay measurements. In addition, the density and depths of both shallow and deep traps change with charging voltage and relative humidity levels. Both shallow and deep trap distribution moves towards lower energy levels, indicating an increase in the film's electrical conductivity.