Large-Scale Molecular Dynamics Simulations of Energetic Ni Nanocluster Impact onto the Surface

On the atomic scale, Molecular Dynamics (MD) Simulation of Nano Ni cluster impact on Ni (100) substrate surface have been carried out for energies of E _a = 1–5 eV/atom and total energy of E _T = 195 eV (the total energy of cluster is E _T = nE _a, n is the number of cluster atoms) to understand quantitatively the interaction mechanisms between the cluster atoms and the substrate atoms. The many-body Embedded Atom Method (EAM) was used in this simulation. We investigated the maximum substrate temperature T _max and the time t _max within which this temperature is reached as a function of cluster sizes and the total energy E _T. The temperature T _max is linearly proportional to total cluster energy. For the constant energy per atom and for the cluster size increase, the correlated collisions rapidly transfers energy to the substrate, and the time t _max approached a constant value. For constant total energy the temperature T _max and the time t _max versus different cluster sizes was studied. We showed that the cluster implantation and sputtering atoms from the surface are affected by the cluster size and total kinetic energy of the clusters. Finally time dependence of the number N _dis of disordered atoms in the substrate was observed.     

Effects of POSS nanoparticles on glass transition temperatures of ultrathin poly(t‐butyl acrylate) films and bulk blends

As a model system, thin films of trisilanolphenyl‐POSS (TPP) and two different number average molar mass (5 and 23 kg mol^?1) poly(t‐butyl acrylate) (PtBA) were prepared as blends by Langmuir–Blodgett film deposition. Films were characterized by ellipsometry. For comparison, bulk blends are prepared by solution casting and the samples are characterized via differential scanning calorimetry. The increase in T_g as a function of TPP content for bulk high and low molar mass samples are in the order of ～10 °C. Whereas bulk T_g shows comparable increases for both molar masses (～10 °C), the increase in surface T_g for higher molar mass PtBA is greater than for low molar mass (～22 °C vs. ～10 °C). Nonetheless, the total enhancement of T_g is complete by the time 20 wt % TPP is added without further benefit at higher nanofiller loads. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 175–182     

Investigation on Adsorption Dynamics of Protein/Tween‐20 Mixture at the Surface of Solution by Surface Pressure Measurement

The dynamic surface tension (γ_t) and apparent diffusion coefficient (D) of nonionic surfactant Tween‐20 in the presence and absence of bovine serum albumin (BSA) have been investigated via the measurements of surface pressure (π) at different time (t). The curves of γ_t～t are obtained from π～t isotherms. Results show that the γ_t～t relationships of Tween‐20 solution with or without BSA accord with the Ward‐Tordai equation in the region of initial adsorption. D value obtained from the γ_t～t^1/2 curves shows that the diffusion of Tween‐20 slows down with the increase of the concentration of Tween‐20 (c _Tween‐20). And D value of Tween‐20 in the presence of BSA is almost the same as that of the system without BSA when c _Tween‐20 is constant, suggesting that the interaction between Tween‐20 and BSA is weak.     

Reactivity in the solid-state between ZnWO<Subscript>4</Subscript> and some rare-earth metal molybdates RE<Subscript>2</Subscript>MoO<Subscript>6</Subscript> (<Emphasis Type="Italic">RE</Emphasis>=Y,Sm, Eu,Gd, Dy,Ho, Er and Lu)

Organic peroxides (OPs) have caused many momentous explosions and runaway reactions, resulting from thermal instability, chemical pollutants, and even mechanical shock. In Taiwan, dicumyl peroxide (DCPO), due to its unstable reactive nature, has caused two thermal explosions and runaway reaction incidents in the manufacturing process. To evaluate thermal hazards of DCPO in a batch reactor, we studied thermokinetic parameters, such as heat of decomposition (†H _d), exothermic onset temperature (T ₀), maximum temperature rise ((dT/dt)_max), maximum pressure rise ((dP/dt)_max), self-heating rate (dT/dt), etc., via differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2).     

Comparative pharmacokinetics studies of benzoylhypaconine,benzoylmesaconine, benzoylaconine and hypaconitine in rats by LC‐MS method after administration of Radix Aconiti Lateralis Praeparata extract and Dahuang Fuzi Decoction

A rapid and sensitive high‐performance liquid chromatography–mass spectrometric (HPLC‐MS) method was developed and validated for simultaneous determination of benzoylhypaconine (BHA), benzoylmesaconine (BMA), benzoylaconine (BAC) and hypaconitine (HA) in rat plasma for the first time. The analytes were separated on a Kromasil C₁₈ column with a total running time of 11 min. The validation data demonstrated a sound feasibility for the newly developed method and it was then applied to the pharmacokinetic study of these analytes in rats. Pharmacokinetic behaviors of BHA, BMA, BAC and HA in rats were studied after oral administration of Radix Aconiti Lateralis Praeparata extract (FZ) and Dahuang Fuzi Decoction (DFD). The main parameters for the two groups of subjects were compared, and significant differences between Radix Aconiti Lateralis Praeparata extract group and Dahuang Fuzi Decoction group in calculated parameters, such as the area under the plasma concentration–time from zero to the last quantifiable time‐point (AUC_0–t), the area under the plasma concentration–time curve from zero to infinity (AUC_0–∞), peak plasma concentration (C_max), half‐life of elimination (T_1/2), mean retention time (MRT_0–t), plasma clearance (CL), volume of distribution (V_d) and time to reach C_max (T_max), were found. After oral administration of DFD, the AUC_0–t, AUC_0–∞ and C_max of BHA, BMA, BAC and HA decreased remarkably (p < 0.05) compared with those of the FZ extract group. V_d and CL values of BHA, BMA, BAC and HA increased, two of which showed significant difference (p < 0.05). T_1/2 and MRT_0–t values of BHA, BMA and BAC in the DFD group were significantly delayed compared with those of FZ extract group. Only the T_max of HA, the toxic ingredient in FZ, delayed significantly in DFD group compared with the value of FZ group. All these pharmacokinetic parameters were statistically compared, and the rationality of the combination for DFD was clearly demonstrated. Copyright © 2013 John Wiley & Sons, Ltd.     

Effects of cumene hydroperoxide on phenol and acetone manufacturing by DSC and VSP2

Cumene hydroperoxide (CHP) being catalyzed by acid is one of the crucial processes for producing phenol and acetone globally. However, it is thermally unstable to the runaway reaction readily. In this study, various concentrations of phenol and acetone were added into CHP for determination of thermal hazards. Differential scanning calorimetry (DSC) tests were used to obtain the parameters of exothermic behaviors under dynamic screening. The parameters included exothermic onset temperature (T ₀), heat of decomposition (ΔH _d), and exothermic peak temperature (T _p). Vent sizing package 2 (VSP2) was employed to receive the maximum pressure (P _max), the maximum temperature (T _max), the self-heating rate (dT/dt), maximum pressure rise rate ((dP/dt)_max), and adiabatic time to maximum rate ((TMR)_ad) under the worst case. Finally, a procedure for predicting thermal hazard data was developed. The results revealed that phenol and acetone sharply caused a exothermic reaction of CHP. As a result, phenol and acetone are important indicators that may cause a thermal hazard in the manufacturing process.     

Thermal hazard evaluation for methyl ethyl ketone peroxide mixedwith inorganic acids

Methyl ethyl ketone peroxide (MEKPO) possesses complex structures which have caused many incidents involving fires or explosions by mixing with incompatible substances, external fires, and others. In this study, reactivities or incompatibilities of MEKPO with inorganic acids (HCl, HNO₃, H₃PO₄ and H₂SO₄) were assessed by differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2). Parameters obtained by the above-mentioned devices could be readily employed to discuss the runaway reaction, such as onset temperature (T ₀), heat of reaction (ΔH _d), time to maximum rate (TMR), maximum self heat rate (dT/dt)_max, adiabatic temperature rise (ΔT _ad), maximum pressure of decomposition (P _max) and so on. Mixing MEKPO with hydrochloric acid resulted in the lowest T ₀ among inorganic acids. Nitric acid not only lowered the T ₀ but also delivered the highest heat releasing rate or self heat rate (dT/dt), which was concluded to be the worst case in terms of contamination hazards during storage or transportation of MEKPO.     

Physical aging in poly(ethylene naphthalene-2,6-dicarboxylate) in relation to sorbed water,enthalpic relaxation,and mechanical properties

Amorphous poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) films (～ 220 μm thick), stored in ambient atmosphere for different periods of time and after annealing at different temperatures below T_g = 123°C, for different times, have been investigated by infrared spectroscopy (FTIR), microhardness, and differential scanning calorimetry (DSC). FTIR spectroscopy and weight measurements reveal the presence of water which is easily removed by annealing of the films. Films again recover their initial weight and absorption bands after 1-2 days storage in ambient atmosphere. Samples annealed at different temperatures T_a for different times t_a show an increasing microhardness for relatively short times of t_a. The microhardness passes through a maximum at an annealing time depending on T_a, and it decreases toward values somewhat larger than the initial ones. The changes observed in the microhardness and in the values of the excess enthalpy with storage time of the samples at room temperature depend on the physical aging as well as on the content of water of PEN films. © 1995 John Wiley & Sons, Inc.     

Developing nonuniform sampling strategies to improve sensitivity and resolution in 1,1-ADEQUATE experiments

Nonuniform sampling (NUS) strategies are developed for acquiring highly resolved 1,1-ADEQUATE spectra, in both conventional and homodecoupled (HD) variants with improved sensitivity. Specifically, the quantile-directed and Poisson gap methods were critically compared for distributing the samples nonuniformly, and the quantile schedules were further optimized for weighting. Both maximum entropy and iterative soft thresholding spectral estimation algorithms were evaluated. All NUS approaches were robust when the degree of data reduction is moderate, on the order of a 50% reduction of sampling points. Further sampling reduction by NUS is facilitated by using weighted schedules designed by the quantile method, which also suppresses sampling noise well. Seed independence and the ability to specify the sample weighting in quantile scheduling are important in optimizing NUS for 1,1-ADEQUATE data acquisition. Using NUS yields an improvement in sensitivity, while also making longer evolution times accessible that would be difficult or impractical to attain by uniform sampling. Theoretical predictions for the sensitivity enhancements in these experiments are in the range of 5–20%; NUS is shown to disambiguate weak signals, reveal some ⁿJ_CC correlations obscured by noise, and improve signal strength relative to uniform sampling in the same experimental time. This work presents sample schedule development for applying NUS to challenging experiments. The schedules developed here are made available for general use and should facilitate the broader utilization of ADEQUATE experiments (including 1,1-, 1,n-, and HD- variants) for challenging structure elucidation problems.     

Ultimate tensile properties of elastomers. VII. Effect of crosslink density on time–temperature dependence

Data on tensile strength and elongation at break for a series of Viton A-HV vulcanizates are discussed. The data were obtained at various extension rates at temperatures from ?5 to 230°C (25 ? T — T_g ? 260°C) on seven vulcanizates having crosslink densities v_e (estimated from C₁ in the Mooney-Rivlin equation) from 0.46 × 10^?5 to 24.4 × 10^?5 mole/cm³. At an extension rate of 1 min^?1, an increase in v_e affects the tensile strength σ_b (based on the undeformed cross-sectional area) and the true tensile strength σ_bσ_b (based on the cross-sectional area of a deformed specimen) as follows: σ_b is essentially constant at a low temperature; it passes through a decided maximum at intermediate temperatures; and it increases to a plateau at elevated temperatures. In contrast, λ_bσ_b decreases markedly at all temperatures, an exception being the most lightly crosslinked vulcanizate(s). Application of time—temperature superposition to the ultimate-property data gave log a_T; its temperature dependence is that typical of nonpolar rubbery polymers. Data on the vulcanizates were compared in corresponding temperature states by plotting log 273σ_b/T, log 273λ_bσ_b/T, and (λ_b — 1)/(λ_b — 1)_max against logt_b/(t_b)_max, where t_b is the temperature-reduced time to break and (t_b)_max is the value at which the ultimate extension ratio λ_b attains its maximum, (λ_b)_max. Except for the most lightly crosslink vulcanizate, the comparison shows that 273λ_bσ_b/T and (λ_b — 1)/(λ_b — 1)_max are substantially independent of (or only weakly dependent on) crosslink density, that 273λ_b/T increases with v_e, and that 273λ_b/T ∝? v_e^0.6 and λ_b ∝? v_e^?0.4 at a large value of t_b/(t_b)_max.     

Isothermal crystallization of concentrated amorphous starch systems measured by modulated differential scanning calorimetry

The slow isothermal crystallization of concentrated amorphous starch systems is measured by Modulated Differential Scanning Calorimetry (MDSC). It can be followed continuously by the evolution (stepwise decrease) of the MDSC heat capacity signal (Cp), as confirmed with data from X-ray diffractometry, Dynamic Mechanical Analysis, Raman spectroscopy, and conventional Differential Scanning Calorimetry. Isothermal MDSC measurements enable a systematic study of the slow crystallization process of a concentrated starch system, such as a pregelatinized waxy corn starch with 24 wt % water and 76 wt % starch. After isothermal crystallization, a broad melting endotherm with a bimodal distribution is observed, starting about 10°C beyond the crystallization temperature. The bulk glass transition temperature (T_g) decreases about 15°C during crystallization. The isothermal crystallization rate goes through a maximum as a function of crystallization time. The maximum rate is characterized by the time at the local extreme in the derivative of Cp (t_max), or by the time to reach half the decrease in Cp (t_1/2). Both t_max and t_1/2 show a bell-shaped curve as a function of crystallization temperature. The temperature of maximum crystallization rate, for the system studied, lies as high as 75°C. This is approximately 65°C above the initial value of T_g. Normalized Cp curves indicate the temperature dependence of the starch crystallization mechanism. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2881–2892, 1999     

Measuring the thermophysical properties of porous fibrous materials with a new unsteady-state method

In this article, the authors first introduced a theoretical model dealing with unsteady-state heat conduction in porous fabric to assess the effects due to local convection during the testing. A few important issues are analyzed including the criterion for local thermal equilibrium in the fibrous materials and the confidence time region (t _min–t _max) during measuring process. The influence due to different heat source capacities can be ignored if the measuring time is greater than the minimum time duration t _min , yet the heat loss via outside surface becomes negligible if the testing duration is below the maximum allowable value t _max. Accordingly an apparatus that can simultaneously measure two thermophysical properties (the thermal conductivity k and thermal diffusivity a) of fibrous materials is developed in this study, which then leads to the determination of the volumetric capacity via ρC = k/a. In order to minimize the influence of potential local micro heat convection and the contact resistance during heat transfer, some background, and stacking materials are adopted in the apparatus. The error range of the apparatus is estimated empirically based on the data from measuring some Perspex samples. Finally four kinds of polyester nonwoven fabrics with different porosities are tested using the device and the data analyzed and compared with theoretical predictions.     

A Novel Thermothickening Aqueous System Prepared from Hydrophobically-Modified Acrylamide Copolymer,Poly(N-isopropylacryl-amide) and Sodium Dodecyl Benzene Sulfonate and Its Mechanism Studies

A new thermothickening aqueous system was presented based on mixtures of hydrophobically-modified acrylamide copolymer (HMPAM), poly(N-isopropylacryl-amide) (PNIPAM) and sodium dodecyl benzene sulfonate (SDBS). Unique in the thermothickening system, a maximum viscosity and the temperature (T _max) when reaching such viscocity change independently, reflects the presence of intermolecular interactions. The T _max of the new system suggests that its thermothickening behavior is correlated to the cloud point temperature (T _c) of PNIPAM, which can be easily adjusted to desired values by the addition of SDBS. The experimental data also indicate that the temperature between the rheological transition temperature (T _t) and T _max in HMPAM+PNIPAM+SDBS is within the range of 35–65°C, and the thermothickening behavior originates from the reinforcement of the association network between HMPAM, PNIPAM and SDBS. Consequently, the viscosity over the corresponding thermosensitive range upon cooling is higher than that upon heating.     

Evaluation of adiabatic runaway reaction of methyl ethyl ketone peroxide by DSC and VSP2

Methyl ethyl ketone peroxide (MEKPO) is generally applied to manufacturing in the polymerization processes. Due to thermal instability and high exothermic behaviors of MEKPO, if any operation is undertaken recklessly or some environmental effect is produced suddenly during the processes, fires and explosions may inevitably occur. In this study, thermal analysis was evaluated for MEKPO by differential scanning calorimetry (DSC) test. Vent sizing package 2 (VSP2) was used to analyze the thermal hazard of MEKPO under various stirring rates in a batch reactor. Thermokinetic and safety parameters, including exothermic onset temperature (T ₀), maximum temperature (T _max), maximum pressure (P _max), self-heating rate (dT dt ⁻¹), pressure rise rate (dP dt ⁻¹), and so on, were discovered to identify the safe handling situation. The stirring rates of reactor were confirmed to affect runaway and thermal hazard characteristics in the batch reactor. If the stirring rate was out of control, it could soon cause a thermal hazard in the reactor.     

Double quantum CRAZED NMR signal in inhomogeneous fields

It has been well accepted that the double quantum (DQ) correlated-spectroscopy revamped by asymmetric z-gradient echo detection (CRAZED) signal is enveloped in the profile function t₂ exp [−(t₂ + 2t₁)/T₂], but this function is too simple to describe the spin echo characteristics of the CRAZED free induction decay signal. In this paper the DQ CRAZED experiment is analyzed by including the homogeneous and inhomogeneous broadening effects, and a formula for the time domain DQ CRAZED signal is obtained. This formula includes the chemical shift echo and the inhomogeneous echo, both appearing at t₂ = 2t₁. Experiments have confirmed the theory.     

Electrochemical nucleation of lead and copper on indium-tin oxide electrodes

The nucleation process of Pb and Cu onto indium-tin oxide electrodes was studied by single potentiostatic steps using 0.1×10^–4 mol L^–1 Cu(NO₃)₂ and 2×10^–2 mol L^–1 Pb(NO₃)₂ solutions in aqueous 1.0 mol L^–1 NaNO₃. The current, I_max, and the time, t_max, corresponding to the maximum, were evaluated by 3D nucleation with a diffusion-controlled growth model for instantaneous and progressive nucleation. The non-dimensional plots of (I/I_max)² vs. t/t_max showed that Cu and Pb nucleation closely followed the response predicted for instantaneous nucleation. Other parameters, such as I vs. t^1/2 and I²_maxt_max, as well as nuclei micrographs, were analyzed, corroborating the results obtained.     

Effect of finite extensibility on the viscoelastic properties of a styrene–butadiene rubber vulcanizate in simple tensile deformations up to rupture

Stress–strain and rupture data were determined on an unfilled styrene–butadiene vulcanizate at temperatures from ?45 to 35°C and at extension rates from 0.0096 to 9.6 min^?1. The data were represented by four functions: (1) the well-known temperature function (shift factor) a_T; (2) the constant strain rate modulus, F(t,T), reduced to temperature T₀ and time t/a_T, i.e., T₀F(t/a_T)/T; (3) the time-dependent maximum extensibility, λ_m(t/a_T); and (4) a function Ω(χ) where χ = (λ ? 1)λ_m⁰/λ_m, in which λ is the extension ratio and λ_m⁰ is the maximum extensibility under equilibrium conditions. The constant strain rate modulus characterizes the stress–time response to a constant extension rate at small strains, within the range of linear response; λ_m is a material parameter needed to represent the response at large λ; and Ω(χ) represents the stress–strain curve of the material in a reference state of unit modulus and λ_m = λ_m. The shift factor a_T was found to be sensibly independent of extension. At all values of t/a_T for which the maximum extensibility is time-independent, the relaxation rate was also found to be independent of λ. These observations indicate that the monomeric friction coefficient is strain-independent over the ranges of T and λ covered in the present study. It was found that λ_m⁰ = 8.6 and that the largest extension ratio at break, (λ_b)_max, is 7.3. Thus, rupture always occurs before the network is fully extended.     

Microcalorimetric investigation of water vapor adsorption on silica gel

In this study, the activities of four ginsenosides Rc, Re, Rd, and Rf on splenic lymphocytes growth were studied by microcalorimetry. Some qualitative and quantitative information, such as the metabolic power–time curves, growth rate constant k, maximum heat-output power of the exponential phase P _max and the corresponding appearance peak time t _max, total heat output Q _t, and promotion rate R _p of splenic lymphocytes growth affected by the four ginsenosides were calculated. In accordance with thermo-kinetic model, the corresponding quantitative relationships of k, P _max, t _max, Q _t, R _p, and c were established, . Also, the median effective concentration (EC₅₀) was obtained by quantitative analysis. Based on both the quantitative quantity–activity relationships (QQAR) and EC₅₀, the sequence of promotion activity was Rc > Re > Rd > Rf. The analysis of structure–activity relationships showed that the number, type, and position of sugar moieties on the gonane steroid nucleus had important influences on the promotion activity of Rc, Re, Rd, and Rf on splenic lymphocytes growth. Microcalorimetry can be used as a useful tool for determining the activity and studying the quantity–activity relationship of drugs on cell.     

Enhancing signal-to-noise ratio and resolution in low-field NMR relaxation measurements using post-acquisition digital filters

The traditional way to enhance signal-to-noise ratio (SNR) of nuclear magnetic resonance (NMR) signals is to increase the number of scans. However, this procedure increases the measuring time that can be prohibitive for some applications. Therefore, we have tested the use of several post-acquisition digital filters to enhance SNR up to one order of magnitude in time domain NMR (TD-NMR) relaxation measurements. The procedures were studied using continuous wave free precession (CWFP-T₁) signals, acquired with very low flip angles that contain six times more noise than the Carr–Purcell–Meiboom–Gill (CPMG) signal of the same sample and experimental time. Linear (LI) and logarithmic (LO) data compression, low-pass infinity impulse response (LP), Savitzky–Golay (SG), and wavelet transform (WA) post-acquisition filters enhanced the SNR of the CWFP-T₁ signals by at least six times. The best filters were LO, SG, and WA that have high enhancement in SNR without significant distortions in the ILT relaxation distribution data. Therefore, it was demonstrated that these post-acquisition digital filters could be a useful way to denoise CWFP-T₁, as well as CPMG noisy signals, and consequently reducing the experimental time. It was also demonstrated that filtered CWFP-T₁ method has the potential to be a rapid and nondestructive method to measure fat content in beef and certainly in other meat samples.     

Zymomonas mobilis as catalyst for the biotechnological production of sorbitol and gluconic acid

The conversion of glucose and fructose into gluconic acid (GA) and sorbitol (SOR) was conducted in a batch reactor with free (CTAB-treated or not) or immobilized cells of Zymomonas mobilis. High yields (more than 90%) of gluconic acid and sorbitol were attained at initial substrate concentration of 600 g/L (glucose plus fructose at 1:1 ratio), using cells with glucose-fructose-oxidoreductase activity of 75 U/L. The concentration of the products varied hyperbolically with time according to the equations (GA)=t(GA)_max/(W_GA +t), (SOR)=t (SOR)_max/(W_Sor+t), v_GA=[W_GA (GA)_max]/(W_GA+t)² and V_SOR=[W_SOR (SOR)_max]/(W_SOR+t)². Taking the test carried out with free CTAB-treated cells as an example, the constant parameters were (GA)_max= 541 g/L, (SOR)_max=552 g/L, W_GA=4.8h, W_SOR=4.9h, υ_GA=112.7 g/L· and υ_SOR=112.7 g/L·.