Τc Values Research Articles

Dynamics of a diffusive model for cancer stem cells with time delay in microRNA-differentiated cancer cell interactions and radiotherapy effects

Understand the dynamics of cancer stem cells (CSCs), prevent the non-recurrence of cancers and develop therapeutic strategies to destroy both cancer cells and CSCs remain a challenge topic. In this paper, we study both analytically and numerically the dynamics of CSCs under radiotherapy effects. The dynamical model takes into account the diffusion of cells, the de-differentiation (or plasticity) mechanism of differentiated cancer cells (DCs) and the time delay on the interaction between microRNAs molecules (microRNAs) with DCs. The stability of the model system is studied by using a Hopf bifurcation analysis. We mainly investigate on the critical time delay τc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ au _{c}$$\\end{document}, that represents the time for DCs to transform into CSCs after the interaction of microRNAs with DCs. Using the system parameters, we calculate the value of τc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ au _{c}$$\\end{document} for prostate, lung and breast cancers. To confirm the analytical predictions, the numerical simulations are performed and show the formation of spatiotemporal circular patterns. Such patterns have been found as promising diagnostic and therapeutic value in management of cancer and various diseases. The radiotherapy is applied in the particular case of prostate model. We calculate the optimum dose of radiation and determine the probability of avoiding local cancer recurrence after radiotherapy treatment. We find numerically a complete eradication of patterns when the radiotherapy is applied before a time t<τc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$t < \ au _{c}$$\\end{document}. This scenario induces microRNAs to act as suppressors as experimentally observed in prostate cancer. The results obtained in this paper will provide a better concept for the clinicians and oncologists to understand the complex dynamics of CSCs and to design more efficacious therapeutic strategies to prevent the non-recurrence of cancers.

Magnetization spiral structure and high domain wall velocity induced by inertial effect

In ultrafast magnetism, i.e., the short time scales such as picosecond and femtosecond, we report that the spiral structure of magnetization can be formed by the inertial effect. Comparing with the case of fast magnetism in nanosecond time scale, we can obtain a higher velocity of domain wall in ultrafast magnetism due to the driving of inertial moment. There is a critical value τc of angular momentum relaxation time τ for the inertial breakdown in uniaxial ferromagnet. Under the action of the inertial effect the domain wall width shows the characteristics of increases firstly as τ<τc, and then decreasing as τ>τc. It directly leads to the positive or negative mobility for the domain wall velocity as the inertia is less than or exceeds the critical value, respectively. In the high frequency mode (i.e., high field mode), we obtain the limit domain wall velocity, i.e., V→1/ατ. The smaller the inertia or damping, the faster the domain wall moves. For the case of biaxial anisotropic ferromagnets, the domain wall width and velocity decreases with the increasing inertia term, respectively. In the presence of inertia effect, there is an another critical magnetic field hc. The domain wall width decreases with the increase of the magnetic field as h<hc, while increases as h>hc. However, the domain wall velocity shows a nearly linear increase with the magnetic field. These results indicate that the ultrafast magnetism has more advantages than fast magnetism. It also provides a good control technique for rapid information processing in the future.

2H-NMR study of molecular reorientation of D2O confined into the slit-shaped micropores of activated carbon fiber

Herein, the reorientation of heavy water (D2O) molecules adsorbed in the slit-type micropores of activated carbon fibers is investigated using the 2H-nuclear magnetic resonance technique. The rotational correlation times (τc) of D2O are evaluated from the 2H spin–lattice relaxation time (T1). The obtained τc values are significantly influenced by both the pore-filling ratio (ϕ) and temperature, thus suggesting that the adsorption of D2O into activated carbon fibers (ACF) effectively influences the reorientation of the D2O molecules within the ACF. The reorientational motion of D2O is examined by the extended jump model. According to this model, the nanoconfinement effect, which results from the reduction in free volume around D2O, is attributed to the transition-state excluded volume effect, whereas the effect of hydrogen bonding between the D2O and surface functional groups is attributed to the transition-state hydrogen bonding effects. Furthermore, the dependence of τc on ϕ is explained by the chemical exchange between the pore surface adsorption sites and the central space of the pore. Thus, the dynamic behavior of adsorbed D2O molecules reveals the mechanism of D2O adsorption into the ACF micropores.

Occurrence state and nuclear magnetic resonance relaxation characteristics of confined water in quartz nanopores

Water in the shale obstructs the enrichment and transportation of shale gas, so it is crucial to identify the occurrence mechanism of water in shale. In this work, molecular dynamics (MD) simulation had been performed to explore the occurrence state, dynamic characteristics, and nuclear magnetic resonance (NMR) relaxation properties of confined water in shale inorganic nanopores (quartz). The results show that the number of adsorbed layers, diffusion coefficients (D) and rotational correlation time (τ c) of water in quartz pores are strongly influenced by pore width (H). Layer analysis of water held in confinement indicates that the D value increases and the τc value decreases as the water approaches the centre of the pore. Furthermore, varying occurrence states lead to different NMR relaxation mechanisms. With the increase of H, the transverse relaxation time of adsorbed water is basically stable at 10−1 s. Finally, an exponential formula for evaluating pore size distribution is established. The total thickness of the water layer with the ratio of the intramolecular relaxation rate to the total relaxation rate less than 40% is defined as the thickness of the adsorbed water film.

Insight into the Molecular Structure, Interaction, and Dynamics of Aqueous Reline Deep Eutectic Solvent: A Nuclear Magnetic Resonance Investigation

Reline, which is composed of choline chloride (ChCl) and urea, is the first and most widely used deep eutectic solvent (DES) described by Abbot and co-workers. Due to the hygroscopic feature, traces of water are unavoidable, which significantly affect the physicochemical properties of reline. At present, the local structure of molecules and the impact from the presence of water are still the most significant questions in this field. Herein, reline and six aqueous dilutions with a controlled amount of water (from 3.2 to 50.0 wt %) were studied mainly by using a combination of nuclear magnetic resonance (NMR) techniques. According to 1D 35Cl NMR, 1D 15N NMR, and 2D 1H-15Cl heteronuclear Overhauser effect spectroscopy, we probed the interactions of urea···Cl- and Ch+···Cl- in pure reline, which gradually dissociated in the presence of water. Moreover, it was revealed that the dissociation rate altered when the water content reached 9.0 wt %, which is ascribed to the higher preference of hydration for Cl- ion compared to other species in the system. Furthermore, selected cross peaks in 1H-1H correlation spectroscopy spectra were analyzed. Accordingly, an enhanced correlation was observed for urea···Ch+ at a lower water fraction within 9.0 wt %. When the water content increased to 24.9 wt %, the water solvation of Ch+ and urea was also observed in COSY spectra. The interaction of H2O···Ch+ got continuously stronger when the water content increased from 24.9 to 50.0 wt %, while H2O···urea got enhanced when the water content reached 33.3 wt % and then diminished gradually from 33.3 to 50.0 wt %. 1H-1H nuclear Overhauser effect spectroscopy and 1H-1H rotating frame Overhauser effect spectroscopy experiments were also conducted for dynamics investigation. The τc value for the species in 9.0 wt % aqueous reline is very close to τccrit of 0.44 ns. For pure reline and the aqueous reline with a water fraction of less than 9.0 wt %, the τc value of the species is longer than 0.44 ns, while for the sample with water of 24.9 wt %, the τc value is much shorter than 0.44 ns. Based on our NMR study, we revealed that with the water amount increasing from 0 to 50.0 wt %, the species involved in the system behaved as the large molecules or molecules in viscous liquids transiting to the medium-sized molecules in nonviscous liquids and finally to small molecules in nonviscous liquids.

WINTER ATMOSPHERIC BLOCKINGS IN THE NORTHERN HEMISPHERE UNDER CLIMATE CHANGES IN RECENT DECADES (1980–2018)

The analysis of winter atmospheric blockings in the Northern Hemisphere (NH) under climate changes in 1980–2018 was carried out. The results of the analysis indicate a significant increase in the total duration of winter atmospheric blockings τ in the NH in recent decades. The noted trend was revealed against the background of a rapid increase in the NH surface air temperature T in winter seasons. The parameter of sensitivity of the atmospheric blockings duration to changes in the NH surface air temperature in winter seasons for the period 1980–2018 was estimated. The statistically significant estimate obtained means an increase in τ by more than one and a half times with an increase in the mean winter surface air temperature of the NH by 1K. A more significant relationship with T was obtained for values of τ above the average value of τc for the period 1980–2018, while at τ τc, the relationship was found to be statistically insignificant. The noted features are associated with differences in different phases of the key modes of climatic variability. In particular, the mean value of the surface air temperature of the NH in winter in the positive phase of the Atlantic Multidecadal Oscillation (AMO) within the analyzed period of 1980–2018 significantly exceeded the corresponding mean value of T in the negative phase of AMO. At the same time, it was found that the mean value of the winter blockings duration in the NH in the positive AMO phase is one and a half times longer than in the negative AMO phase. For winter seasons, the estimates of the relationship between τ and the intensity of the Arctic anticyclonic center of action depending on the AMO phase were obtained.

Exploring Molecular Dynamics of Adsorbed CO2 Species in Amine-Modified Porous Silica by Solid-State NMR Relaxation.

Previous studies on CO2 adsorbents have mainly addressed the identification and quantification of adsorbed CO2 species in amine-modified porous materials. Investigation of molecular motion of CO2 species in confinement has not been explored in depth yet. This work entails a comprehensive study of molecular dynamics of the different CO2 species chemi- and physisorbed at amine-modified silica materials through the determination of the rotating frame spin–lattice relaxation times (T1ρ) by solid-state NMR. Rotational correlation times (τC) were also estimated using spin relaxation models based on the Bloch, Wangsness, and Redfield and the Bloembergen–Purcell–Pound theories. As expected, the τC values for the two physisorbed CO2 species are considerably shorter (32 and 20 μs) than for the three identified chemisorbed CO2 species (162, 62, and 123 μs). The differences in molecular dynamics between the different chemisorbed species correlate well with the structures previously proposed. In the case of the physisorbed CO2 species, the τC values of the CO2 species displaying faster molecular dynamics falls in the range of viscous liquids, whereas the species presenting slower dynamics exhibit T1ρ and τC values compatible with a CO2 layer of weakly interacting molecules with the silica surface. The values for chemical shift anisotropy (CSA) and 1H–13C heteronuclear dipolar couplings have also been estimated from T1ρ measurements, for each adsorbed CO2 species. The CSA tensor parameters obtained from fitting the relaxation data agree with the experimentally measured CSA values, thus showing that the theories are well suited to study CO2 dynamics in silica surfaces.

Comparison of Critical Shear Stress of Rill Erosion Estimated from Two Methods

Various disputes exist regarding the critical shear stress (τc) of rill erosion determined by linear regression. Alternatively, some researchers have attempted to measure critical shear stress (τo) of rill erosion by observing the start of soil particle detachment and showed promising results. However, few studies have been conducted to evaluate the reliability of the method determining τo. Thus, this study was conducted to identify the reliability of the method determining τo by comparing the values of τc and τo and their relationships with rill erodibility (Kr) and influencing factors, using 360 disturbed soil samples (standing for the freshly tilled condition) from six sampling sites along a 330 km transect in the Loess Plateau. Results indicated that the mean τc was 1.90 times greater than that of τo. No significant relationship was found between τc and Kr. An inverse changing trend between Kr and τo was observed from Yijun to Zizhou, while both Kr and τo exhibited increasing trends from Zizhou to Yulin. The τo of six sampling sites all demonstrated increasing trends with slope gradient (S), which contradicted the statement of the WEPP model that τc was independent of S. The relationships between τc and the measured soil properties were poor, whereas the τo increased exponentially with soil organic matter. Generally, τo did not present significantly better results than τc; the reliability of τo also showed some uncertainties, such as the subjective judgment of the beginning detachment of soil particles. This result has great importance for deepening our understanding of the rill erosion mechanism.

Seasonal variation in soil erosion resistance to overland flow in gully-filled farmland on the Loess Plateau, China

Large areas of farmland have been established in China’s Loess Plateau region by backfilling forest and grasslands in gullies with topsoil from hillslopes. High amounts of plant litter are incorporated into the topsoil during such processes; however, their effects on soil erosion resistance under natural conditions are not fully understood. Therefore, the present study investigated seasonal variation in soil erosion resistance to overland flow and the underlying factors in the gully-filled farmland. Two typical plant litter species were selected in this study, i.e., Artemisia sacrorum Ledeb. (ASL) and Bothriochloa ischaemum (L.) Keng. (BIL). Overland water flow was tested under six shear stress levels (5.66–22.11 Pa) in natural soil samples incorporated with plant litter and without plant litter to determine soil erosion resistance parameters (rill erodibility Kr and critical shear stress τc). The study was conducted over 524 days (through May 6, 2017, to October 11, 2018), covering two rainy seasons and one winter. Soil properties changed significantly over time, with physical crust thickness and cohesion increasing from 0 to 10.7 mm and 2.9–13.4 kPa, respectively. In contrast, the mass density of incorporated plant litter decreased from 0.7 to 0.2 kg m−2. Soil erosion resistance increased with time, which showed that Kr decreased (from 0.516 to 0.021 s m−1) and τc increased (from 0.49 to 7.98 Pa). Compared with the initial state of new farmland (Kr = 0.507 s m−1,τc= 0.48 Pa), Kr decreased by 77–96% and τc increased 8–14 times at the end of the study. Plant litter incorporation markedly enhanced soil erosion resistance in a time- and species-dependent manner. Compared with the bare soil without plant litter, the Kr values of ASL and BIL treatments were 3–64% and 2–83% lower, and their τc values were 0–81% and 0–55% higher, respectively. Kr was significantly and positively correlated with cumulative precipitation, cumulative rainfall kinetic energy, soil cohesion, and physical soil crust thickness, while τc was negatively correlated with the influencing factors. Further, both Kr and τc could be well predicted by physical soil crust thickness and cohesion (R2 = 0.79 and 0.87, p < 0.01, n = 27). According to the results, seasonal patterns of soil erosion resistance in the gully-filled farmland established under plant litter incorporation were mainly controlled by rainfall and physical soil crust structure. This study provides a reference resource for soil erosion prediction in farmland ecosystems on the Loess Plateau.

Dissecting Monomer-Dimer Equilibrium of an RNase P Protein Provides Insight Into the Synergistic Flexibility of 5' Leader Pre-tRNA Recognition.

Ribonuclease P (RNase P) is a universal RNA-protein endonuclease that catalyzes 5’ precursor-tRNA (ptRNA) processing. The RNase P RNA plays the catalytic role in ptRNA processing; however, the RNase P protein is required for catalysis in vivo and interacts with the 5’ leader sequence. A single P RNA and a P protein form the functional RNase P holoenzyme yet dimeric forms of bacterial RNase P can interact with non-tRNA substrates and influence bacterial cell growth. Oligomeric forms of the P protein can also occur in vitro and occlude the 5’ leader ptRNA binding interface, presenting a challenge in accurately defining the substrate recognition properties. To overcome this, concentration and temperature dependent NMR studies were performed on a thermostable RNase P protein from Thermatoga maritima. NMR relaxation (R1, R2), heteronuclear NOE, and diffusion ordered spectroscopy (DOSY) experiments were analyzed, identifying a monomeric species through the determination of the diffusion coefficients (D) and rotational correlation times (τc). Experimental diffusion coefficients and τc values for the predominant monomer (2.17 ± 0.36 * 10−10 m2/s, τ c = 5.3 ns) or dimer (1.87 ± 0.40* 10−10 m2/s, τ c = 9.7 ns) protein assemblies at 45°C correlate well with calculated diffusion coefficients derived from the crystallographic P protein structure (PDB 1NZ0). The identification of a monomeric P protein conformer from relaxation data and chemical shift information enabled us to gain novel insight into the structure of the P protein, highlighting a lack of structural convergence of the N-terminus (residues 1–14) in solution. We propose that the N-terminus of the bacterial P protein is partially disordered and adopts a stable conformation in the presence of RNA. In addition, we have determined the location of the 5’ leader RNA in solution and measured the affinity of the 5’ leader RNA–P protein interaction. We show that the monomer P protein interacts with RNA at the 5’ leader binding cleft that was previously identified using X-ray crystallography. Data support a model where N-terminal protein flexibility is stabilized by holoenzyme formation and helps to accommodate the 5’ leader region of ptRNA. Taken together, local structural changes of the P protein and the 5’ leader RNA provide a means to obtain optimal substrate alignment and activation of the RNase P holoenzyme.

Evaluating high pressure-treated corn and waxy corn starches as novel fat replacers in model low-fat O/W emulsions: A physical and rheological study

High hydrostatic pressure-treated corn starch (HPCS) and waxy corn starch (HPWCS) at three concentrations (10%, 15%, and 20%) were applied as novel fat replacers in a model low O/W emulsion at three fat reduction levels (FR, 25%, 50%, and 75%) and some physical, textural and rheological characteristics and stability of the samples were examined and compared with the control. Applying higher concentrations of HPCS and HPWCS increased the zeta potential, hardness and consistency (mainly for HPWCS samples), reversely decreased the Z-average particle size and polydispersity index of the reduced-fat emulsions, but augmenting FR levels caused a reverse inclination. The rheological assay cleared that the emulsions prepared with HPWCS had greater elastic modulus (G′) and more gap between G′ and viscous modulus (G″) at all concentrations than the HPCS-contained samples. The critical stress (τc) of 25FR samples were significantly higher than the control, showing the well stability of reduced-fat samples. Also, the τc of the HPCS-contained emulsions reduced meaningfully when the FR level increased from 25% to 75%, but for the HPWCS samples, fat reduction didn't change the τc value significantly up to 50% fat reduction. Based on Tangδs(n−LVE), HPWCS contained samples showed more spreadability than the HPCS-contained emulsions.

Temporal Simulation of Sediment Yield Using WEPP Model in Dal Catchment of Temperate Region of Kashmir Valley, India: Case Study

Soil erosion by water is a serious and continuing environmental problem. In the present study the Water Erosion Prediction Project (WEPP) model was used in the Dal catchment to simulate sediment yield. The study was conducted with the objective of calibrating and validating WEPP at the plot scale to examine its suitability for conservation planning. The WEPP model was calibrated using modified input parameters; further, the results were validated using a different data set. The soil erodibility (Kd) and critical shear stress (τc) values vary from 1.70–2.7 and 0.27–0.76 Pa, respectively, for the study area. The average annual sediment yield (hillslope 1 and hillslope 2) was 6.759 t ha−1 as against the measured value of 5.623 t ha−1. The modeled values of sediment yield showed a close agreement with field observed values. The model also produced temporal variations of sediment yield on hillslope areas. The correlation coefficients were found to be 0.93 and 0.945, RMSE were 0.065 and 0.06 t ha−1, and Nash-Sutcliffe efficiency indexes were 0.84 and 0.85 for the validation and calibration periods, respectively. The coefficient of determination (R2) values were found to be 0.89 and 0.90 during calibration and validation of the model, respectively. Results indicated that the WEPP model simulated sediment yield from steep slope conditions and in forest conditions as well. The WEPP model was found to be an effective tool for simulating hydrological and soil erosion processes in watersheds having scarce data.

Behavior of soil erodibility parameters due to biological soil crusts using jet erosion tests

Biological soil crusts (biocrusts) are generally found in many landscapes. Biocrusts are known to have a key role in terms of soil stabilization but the mechanism of biocrusts is poorly understood. Thus, this work intends to examine the impact of two biocrusts: Cyanobacteria and Chlorophyte, on parameters of cohesive soil erodibility (erodibility coefficient, kd, and critical shear stress, τc) using a small-scale form of Jet Erosion Test (mini-JET) at different drying times. In addition, the study aims to develop relationships between τc and kd versus certain soil characteristics. Eighteen undisturbed soil samples of two biocrust types Cyanobacteria, and Chlorophyte, and bare soils were acquired from the banks of the Tigris River in Iraq, and were tested in a laboratory using a mini-JET at drying times of 5, 8, and 12 days, in order to mimic field conditions. It was observed that dead algae still adhered to and bound soil particles together throughout the observation period, which contributed to soil stability, and increased moisture and nutrient retention before decomposition. As the drying times increased in the two biocrusts, the statistical results showed a reduction in kd, while τc values increased. The kd decreased as salt concentration, organic matter, and calcium carbonate increased, while the τc increased. No change in pH levels of soil was observed due to the reactions in the biocrusts between the algal crust and soil particles, which increased organic matter and calcium carbonate. This study discusses the benefits of using a JET instrument; including reducing testing time, conserving energy, and providing low-cost method for observation of crusted soil stabilization, in comparison with previous techniques.

Experimental investigations on single-phase convection and critical heat flux in vertical tubes under oscillatory flow condition

Experimental investigations on single-phase convection and critical heat flux in a vertical tube with an inner diameter of 6.0 mm under inlet flow oscillation conditions were carried out for the following range: 255 ≤ Gav ≤ 455 kg·m−2·s−1, 0.5 ≤ P ≤ 3.0 MPa, 0 < ΔG/Gav ≤ 3.0 and 0 < τ (period of flow oscillation) ≤ 10.6 s. Single-phase convective results show that the fluctuation amplitude of single-phase pressure drop decreases with an increasing τ. Besides, there may be a critical value τc. The average value of wall temperature under steady state condition is smaller than that under oscillatory flow condition when τ > τc while the former is larger than the latter when τ < τc. With respect to two-phase results, the effect of flow oscillation on fluctuation amplitude of wall temperatures under flow boiling conditions is quite small. In addition, flow oscillation deteriorates flow boiling heat transfer in vertical tubes to some extent when 1.04 ≤ τ ≤ 10.6 s. The normalized periodic CHF (Fp) decreases with an increasing average mass velocity, especially for short periods of flow oscillation. In addition, the declining rate of Fp as a function of ΔG/Gav was decayed with an increasing period of flow oscillation. In a general, 2006 CHF lookup-table and Kim et al. correlation are recommended to calculate CHF under steady state condition and periodic dryout heat flux under inlet flow sinusoidal oscillation condition, respectively.

Lipid chain mobility and packing in DOPC bilayers at cryogenic temperatures

Low-temperature molecular mobility and packing in biological tissues are important for their survival upon cryopreservation. Electron paramagnetic resonance (EPR) in its pulsed version of electron spin echo (ESE) allows studying stochastic librations of spin-labeled molecules, the type of motion which dominates at low temperatures. These librations are characterized by the parameter <α2>τc where <α2> is the mean squared angular amplitude and τc is the correlation time for the motion. This parameter is known to be larger for higher temperature and for looser intermolecular structure. In this work, ESE data for the bilayers comprised of doubly-unsaturated DOPC (dioleoyl-glycero-phosphocholine) lipids and mono-unsaturated POPC (palmitoyl-oleoyl-glycero-phosphocholine) lipids with spin-labeled stearic acids added were obtained in the temperature range between 80 and 210 K; the results were compared also with the previously obtained data for fully-saturated DPPC (dipalmitoyl-glycero-phosphocholine) lipid bilayers [J. Phys. Chem. B2014, 118, 12,478–12,485; Appl. Magn. Reson. 2018, 49, 1369–1383]. It turned out that for DOPC bilayers the <α2>τc values are of intermediate magnitude between those for POPC and DPPC bilayers, which implies an intermediate density of lipid packing. A possible explanation of this result could be rearrangement at cryogenic temperatures of the DOPC lipid tails, with their terminal segments folding cooperatively. This interpretation is also in agreement with the known thermodynamic properties of gel-fluid transition for DOPC bilayer.

Quantifying Soil Erodibility Parameters Due to Wastewater Chemicals

Many factories and hospitals dumped their wastewater into Tigris River without any treatment in Baghdad city. This could influence on soil erodibility on Tigris Riverbanks. Phenol, Nitrate, and Phosphate were considered as huge concentrations in wastewater chemicals. The main objectives of this research were: 1) to investigate the influence of three wastewater chemicals on erodibility parameters of cohesive soils using Blaisdell's solution and scour depth solution techniques from jet erosion tests (JETs); 2) to develop relationship between erodibility parameters and soil hardness. An excess shear stress model was utilized to measure soil erodibility based on two empirical soil parameters: critical shear stress (τc) and erodibility coefficient (kd). The results showed a constantly increased in kd for all three wastewater chemicals at different curing times and concentrations, while τc values were decreased. An inverse relationship was developed between τc and kd for both Blaisdell's solution and scour depth solution techniques.

An Assessment of Eddy-Covariance-Based Surface Fluxes Above an Evaporating Heated Surface Under Fair-Weather Daytime Conditions

Above an evaporating heated surface under fair-weather daytime conditions, the cospectra between the vertical velocity component, temperature, and water-vapour mixing ratio should be positive. We have applied a multi-resolution technique to a 3.64-h long, 10-Hz time series centred at midday for 16 fair-weather days at a mid-latitude site during spring to measure the averaging period τc at which the crossover from the domain of the three positive cospectra to a mixed-sign domain occurs. The τc values broadly range from 9 to 42 min, with 13 of the 16 days having values less than 30 min. When mesoscale circulations induced by surface heterogeneity are likely to be present, the vertical heat (or moisture) flux computed with the conventional averaging period of 30 min τ30 is as large (or small) as 1.09 (or 0.78) times that using τc. However, on 14 (or 13) days, the vertical heat (or moisture) fluxes using the period τc are explained by those calculated with the period τ30 within a difference range of ± 1%. The insignificant difference is due to the insensitivity of the fluxes to the averaging period at scales larger than approximately 7 min. Therefore, despite a broad range of τc values, the 30-min-averaged surface fluxes can be treated as the required turbulent fluxes. Although this finding is not robust, given that data were collected at one location over 16 days, it supports the use of 30-min-averaged surfaces fluxes, particularly for the composite midday fluxes on fair-weather days.

Design of half-car active suspension system for passenger riding comfort

In this paper, the active suspension system is designed to reduce vibration on the passenger seat caused by change in road-surface shapes or disturbance. PID control is utilized in the design of this active suspension system, and Direct Synthesis method is proposed to tune PID parameters. Direct Synthesis method optimize PID tuning parameters to achieve desired output response in different road surface. In this study, three interference signals are used as disturbance from surface road i.e step, impulse, and sinus. The aim of the suspension control design is to obtain the control parameters that conform to ISO 2631. The simulation results show that value of τc 0.0002 for step disturbance provide aRMS 0.086 m/s2 and damping ratio 0.21. For impulse input the value of τc 0.002 provide aRMS 0.112 m/s2 and damping ratio of 0.22. For sinus input value of τc 0.00005 provide aRMS 0.09 m/s2.

VO2 thin films with low phase transition temperature grown on ZnO/glass by applying substrate DC bias at low temperature of 250 °C

High-performance vanadium dioxide films with low phase transition temperatures of 40–50 °C were successfully fabricated by applying various negative substrate bias voltages at a low substrate temperature of 250 °C. This low-temperature preparation method and the films’ thermochromic properties may provide useful suggestions for industrial production of VO2 films for smart window applications. The effects of the negative substrate dc bias voltage on the microstructure, surface morphology, and optical and electrical performance of the VO2 films were characterized. X-ray diffraction showed that the residual compressive stress in the films increased as the substrate bias increased, and the maximum value can reach −576 MPa. Temperature-dependent sheet resistance measurement showed that the transition temperature (τc) and room-temperature sheet resistance decreased significantly with increasing substrate bias, and the lowest value of τc is 38.5 °C. The calculated solar energy modulation ability (ΔTsol) of the VO2 film fabricated under a substrate bias voltage of −175 V at 250 °C is approximately 9.73%, which may indicate strong potential for application in smart energy-efficient windows produced industrially at a low substrate temperature.

Decoupling the Effects of Transport and Chemical Loss on Tropospheric Composition: A Model Study of Path‐Dependent Lifetimes

AbstractThe distribution of most trace species within the troposphere depends on a complex interplay between chemistry and transport. Holzer and Waugh (2015) introduced the concept of a path‐dependent lifetime τc(r), that parameterizes the integrated chemical loss during transport from the source to a given location r. Here we examine whether this parameterization provides a new approach for decoupling transport and chemistry. We present calculations of path‐dependent lifetimes for a suite of chlorofluorocarbon replacement gases in a simple 12‐box model and show that for trace species with global lifetimes from 0.5 years to 50 years τc provides an accurate representation of the integrated chemical loss during transport. The value of τc is shown to be sensitive to tropical hydroxyl radical (OH) concentrations, with much weaker sensitivity to extratropical OH or transport. Furthermore, fractional changes in Southern Hemisphere extratropical τc are similar to the corresponding fractional changes in tropical OH; that is, a 10% increase in tropical OH results in a 10% decrease in τc. This suggests that observation‐based estimates of τc may be used to constrain tropical OH concentrations provided that τc can be determined with sufficient precision.