Constant Plateau Value Research Articles

SN1987A constraints to BSM models with extra neutral bosons near the trapping regime: U(1)Lμ−Lτ model as an illustrative example

New physics beyond the Standard Model (BSM) with an extra neutral boson can be constrained from the observation of SN1987A, since productions of this neutral boson in a supernova (SN) could accelerate the SN cooling and potentially lead to a period of the neutrino burst incompatible with the observation. The constraint to the model is formulated by the condition LNB≤3×1052 erg/s according to Raffelt with LNB the luminosity of BSM neutral boson. Computing the above luminosity in the large coupling case, the so-called trapping regime, is nontrivial since the luminosity is a competition between the large production rate and the efficient absorption or decay rate of the neutral boson. We illustrate such a subtlety using U(1)Lμ−Lτ model as an example where the Z′ luminosity, LZ′, from the neutrinosphere is calculated. We calculate Z′ production, absorption, and decay rates through pair-coalescence, semi-Compton, loop-bremsstrahlung from proton-neutron scattering, and their inverse processes in a benchmark SN simulation with muons. We point out that, as the coupling constant gZ′ increases, LZ′ shall be approaching to a constant plateau value for a given mZ′ instead of monotonically decreasing down to zero as obtained in the previous literature. We demonstrate that this plateau phenomenon can be understood by physical arguments and justified by numerical calculations. With a different result on LZ′ from the previous one, we discuss impacts on the constraints to U(1)Lμ−Lτ parameter space by SN1987A. The implication of our result to the similar constraint on a generic BSM model with an extra neutral boson is also discussed. Published by the American Physical Society 2024

Shear Thicking and Impact Resistance Properties of STG in Flexible Protection Application

The rheological properties of shear thickening gel(STG) and its application as protective composite were studied in the paper. Upon applying a shear stress with excitation frequency from 1 Hz to 100 Hz, the storage modulus (G’) of the STG increases from 101 Pa to 105 Pa, demonstrating an excellent shear thickening effect. The reduction of temperature increases the G’min of STG, but when the temperature reaches at 50°C, the G’ curve shows a moderate slope and a gradual transition to the constant plateau value. By introducing STG into polyurethane foam and kevlar fiber with dip and dry method, successfully fabricate a nove safeguarding polymer composite. The protective performance of composite protective materials was studied by static compression experiment and drop hammer impact experiment. The addition of STG increases the impact resistance and puncture resistance of PU and kevlar by at least two times. The materials shows excellent shear stiffening effect, creep resisting and impact resistant propertie.

(Invited) Complementary Experimental and Modeling Approaches to Elucidate Critical Conditions for Pit Stability and Repassivatio

Robust life prediction models for metallic assets exposed to corrosive environments generally employ a maximum damage size criterion as a design parameter. Such models are particularly useful for use in systems such as compressor blades on carrier-based aircraft, offshore platforms, and radioactive waste storage containers1. Stainless steel, which is often used in these cases, is resistant to general corrosion in such environments, but susceptible to localized corrosion due to the galvanic couple that occurs between the actively dissolving pit and the cathode surrounding it. These galvanic characteristics allow for the critical conditions for each electrode to be analyzed separately as functions of corrosion geometry and then combined through the conservation of charge to determine the maximum damage size2,3. It is imperative therefore to accurately identify and measure the critical conditions for both the anode and the cathode, so that the resulting prediction correctly estimates the maximum damage size for a given system. Galvele’s stability criterion4, which describes the steady-state flux arising out of the competition between metal dissolution and diffusion in the pit, governs the anodic stability conditions, and expresses the anodic current density as a function of the pit depth. For the cathodic reaction, the physical chemistry of the electrolyte and details of the immersion conditions (fully immersed or thin film) specify the constraints leading to the assessment of ohmic drop and cathodic kinetics on the metal surface. When combined, these expressions permit the estimation of the maximum size a pit that initiates in this system is likely to grow to, its propagation limited by the cathodic current available to support it. A comprehensive, quantitative electrochemical framework that unifies the critical conditions describing pit stability and repassivation necessitates a relationship between the measured parameters to the chemical conditions at the corroding surface. Diffusion modeling of a one-dimensional pit employed for this purpose shows that the concentration of the cation at the corroding surface can be expressed as a fraction of the concentration at saturation in terms of time and pit depth. Correspondingly, the time to dilution of the surface from 100% saturation to any fraction f can also be calculated from this expression. When this time variable is compared to the experimental time between the surface states of the salt film and repassivation and then juxtaposed with the minimum depth at which the repassivation potential reaches a constant plateau value, an estimate of the critical surface concentration is obtained.5,6 The artificial pit can also be utilized to determine the pH associated with the critical surface concentration. Rapid anodic kinetics were performed at different surface concentrations as determined by the time to dilution from model calculations following the attainment of a predetermined pit depth. These experiments provide data that show how the dissolution kinetics change as the surface concentration approaches the critical value, where a distinct active-passive transition is observed. Tafel extrapolation of the anodic kinetics at this critical surface concentration in combination with cathodic kinetics for the hydrogen evolution reaction provides an estimate of the local cathodic reaction’s contribution towards repassivation. A map of the local cathodic reaction fraction versus pH can be obtained from an analysis of the varying degrees of hydrolysis to estimate the pH at the critical surface concentration. Such an analysis permits an estimate of the critical pH as the pit transitions from active dissolution to repassivation. Chemical simulations based on solution thermodynamics indicate that repassivation at the critical pH occurs as a result of the nucleation of specific oxides, which provide quantitative support to the view formulated by Okada7 and Sridhar et al.8 This presentation will describe the quantitative framework, the experimental and modeling results that support it, and its utility for the long-term prediction of pitting damage.

How does hydration affect the mechanical properties of wine stoppers?

Data related to the comparison of the mechanical properties of the different stoppers used in the wine industry are scarce. This study aims at comparing the effect of hydration (from 0 to 100 % relative humidity at 25 °C) on the mechanical properties of four widely used types of stoppers: natural corks, agglomerated corks, technical stoppers and synthetic (co-extruded) stoppers. For both natural and agglomerated corks, the Young’s modulus was significantly and similarly affected by hydration, with a constant plateau value up to 50 % relative humidity (RH) and a mean value around 22 and 14 MPa, respectively. For higher RH, the increase in water content leads to a decrease in the material rigidity (Young’s modulus <10 MPa), which is attributed to water clusters formation between polymer chains. Technical stoppers revealed a similar profile, but with a much smaller impact of the water content and with overall lower Young’s moduli values, around 5 MPa, throughout the RH range. The stiffness of synthetic closures was not affected by hydration, in agreement with the hydrophobic behavior of polyethylene. Differential scanning calorimetry and dynamic mechanical thermal analysis allowed us to identify a glass transition temperature (Tg) in cork (around 0 °C), and another one in agglomerated cork and technical stoppers (close to −45 °C, corresponding to additives). All together, for the first time the data highlight the comparative mechanical properties of such materials of the wine industry, and the progressive loss of the “cork-like” behavior of cork composites when other components are mixed with cork.

Rheological Properties of SP in Shock Transmission Application

AbstractThe rheological properties of silly putty (SP) and its application as a shock transmission unit (STU) were studied in the paper. By using a parallel-plate rheometer, the frequency sweep at different temperature was carried out to investigate the rheological properties of SP. For all test temperatures, the complex viscosity of SP shows shear thinning, but the G′-curve shows a moderate slope and a gradual transition to the constant plateau value. And once the angular frequency exceeds a critical value, the storage modulus will exceed the loss modulus under the condition of all temperatures. Two prototypes of STU were fabricated with SP and their mechanical performances were experimentally evaluated. The results of the slow movement test and the simulated dynamic test show that the STU can provide a free motion under slowly applied loads and a rigid link under impact loads.

Time-Dependent Shear-Induced Nonlinear Viscosity Effects in Dilute CTAC/NaSal Solutions: Mechanism Analyses

The time-dependent shear-induced nonlinear viscosity effects of dilute surfactant solutions (CTAC/NaSal) at constant shear rate were tested by using the rheometer Couette cell. The apparent viscosity evolution curve can be divided into five stages: weak shear-thickening (Stage I), weak shear-thinning and plateau (Stage II), sharp shear-thickening (Stage III), oscillating adjustment (Stage IV), and rough plateau (Stage V). In Stage I, the stretching effects of shear flow lead to the weak increase in apparent viscosity at the inception of shearing. The apparent viscosity curve firstly decreases in Stage II and then levels off. The apparent viscosity plateau is caused by the forming and slipping of micellar lumps at the inner cylinder wall surface. Once the volume of lump exceeds a certain degree, the nucleation process of forming SIS is triggered, which is the beginning of Stage III and then the apparent viscosity increases sharply. The variations of apparent viscosity in adjusting period are rather complicated in Stage IV, and the variations mainly depend on the situation of SISs network. In Stage V, coupled with obvious oscillations, the apparent viscosity maintains a basically constant plateau value, indicating that the SISs network is fully developed and saturated at the corresponding shear rate.

Experimental velocity fields and forces for a cylinder penetrating into a granular medium

We present here a detailed granular flow characterization together with force measurements for the quasi-bidimensional situation of a horizontal cylinder penetrating vertically at a constant velocity in dry granular matter between two parallel glass walls. In the velocity range studied here, the drag force on the cylinder does not depend on the velocity V(0) and is mainly proportional to the cylinder diameter d. While the force on the cylinder increases with its penetration depth, the granular velocity profile around the cylinder is found to be stationary with fluctuations around a mean value leading to the granular temperature profile. Both mean velocity profile and temperature profile exhibit strong localization near the cylinder. The mean flow perturbation induced by the cylinder decreases exponentially away from the cylinder on a characteristic length λ that is mainly governed by the cylinder diameter for a large enough cylinder/grain size ratio d/d(g): λ~d/4+2d(g). The granular temperature exhibits a constant plateau value T(0) in a thin layer close to the cylinder of extension δ(T(0))~λ/2 and decays exponentially far away with a characteristic length λ(T) of a few grain diameters (λ(T)~3d(g)). The granular temperature plateau T(0) that scales as V(0)(2)d(g)/d is created by the flow itself from the balance between the "granular heat" production by the shear rate V(0)/λ over δ(T(0)) close to the cylinder and the granular dissipation far away.

Increase in passive stiffness at reduced airway smooth muscle length: potential impact on airway responsiveness

The amplitude of strain in airway smooth muscle (ASM) produced by oscillatory perturbations such as tidal breathing or deep inspiration (DI) influences the force loss in the muscle and is therefore a key determinant of the bronchoprotective and bronchodilatory effects of these breathing maneuvers. The stiffness of unstimulated ASM (passive stiffness) directly influences the amplitude of strain. The nature of the passive stiffness is, however, not clear. In this study, we measured the passive stiffness of ovine ASM at different muscle lengths (relative to in situ length, which was used as a reference length, L(ref)) and states of adaptation to gain insights into the origin of this muscle property. The results showed that the passive stiffness was relatively independent of muscle length, possessing a constant plateau value over a length range from 0.62 to 1.25 L(ref). Following a halving of ASM length, passive stiffness decreased substantially (by 71%) but redeveloped over time ( approximately 30 min) at the shorter length to reach 65% of the stiffness value at L(ref), provided that the muscle was stimulated to contract at least once over a approximately 30-min period. The redevelopment and maintenance of passive stiffness were dependent on the presence of Ca(2+) but unaffected by latrunculin B, an inhibitor of actin filament polymerization. The maintenance of passive stiffness was also not affected by blocking myosin cross-bridge cycling using a myosin light chain kinase inhibitor or by blocking the Rho-Rho kinase (RhoK) pathway using a RhoK inhibitor. Our results suggest that the passive stiffness of ASM is labile and capable of redevelopment following length reduction. Redevelopment and maintenance of passive stiffness following muscle shortening could contribute to airway hyperresponsiveness by attenuating the airway wall strain induced by tidal breathing and DI.

Thermal Diffusion of Dilute Polymer Solutions: The Role of Chain Flexibility and the Effective Segment Size

We have investigated the influence of the chain length and the size of the Kuhn segment on the thermal diffusion coefficient DT of dilute solutions of polymers in organic solvents. For oligomers and short polymer chains, DT increases with molar mass M and reaches a molar mass independent constant plateau value. A similar increase and plateau is observed for high polymers with increasing chain stiffness. For chains with Kuhn segments above 1 kg/mol, the plateau value is independent of the polymer and inversely proportional to the solvent viscosity. The thermal diffusion coefficient of such a polymer can be estimated to be DT ≈ 0.6 × 10−14 Pa m2 K−1 × η−1. No simple relation holds for short chains and flexible high polymers.

Interfacial and foaming properties of sulfydryl-modified bovine β-lactoglobulin

The effects of a control blocking of free cystein by N-ethylmaleimide on the interfacial behavior (kinetics of adsorption at the air/water interface, rheology of the interfacial layer) as well as on the foaming properties (density, stability) of β-lactoglobulin were investigated. Compared to native β-lactoglobulin (unmodified β-lactoglobulin), sulfydryl-modified β-lactoglobulin exhibited higher surface hydrophobicity, adsorbed faster at the air/water interface, had the capability to develop rapidly an interfacial layer with high shear elastic constant but exhibited a considerably lower shear elastic constant plateau value. Moreover, sulfydryl-modified β-lactoglobulin exhibited better foaming properties especially regarding the short-term foam stability suggesting that the initial rheology of the interfacial film is at least as much important for the general mechanism of foam stabilization as the potential viscoelasticity the interfacial film could reach on aging.

Dark cure studies of cationic photopolymerizations of epoxides: Characterization of kinetic rate constants at high conversions

AbstractThe effective propagation rate constant (kp; averaged over all the propagating active centers) was characterized for solvent‐free cationic photopolymerizations of phenyl glycidyl ether over the entire range of conversions, including the high conversion regime in which mass transfer limitations become important. The profile for the kp as a function of conversion was found to exhibit a constant plateau value at low to intermediate conversions, followed by a monotonic increase above a threshold value of conversion. To explain this trend, it is proposed that at high conversion the diffusional mobility of the photoinitiator counterion is reduced whereas the mobility of the cationic active center remains high because of reactive diffusion. Therefore, with increasing conversion, the average distance between the active centers and counterions may increase, resulting in an increase in the propagation rate constant. The profiles for the kp values were investigated as a function of the temperature, photoinitiator anion, and photoinitiator concentration. As the photoinitiator concentration was increased, the plateau value of the effective propagation rate constant decreased whereas the threshold conversion increased. All of the experimental trends are consistent with the proposed increase in ion separation at high conversions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4409–4416, 2004

Transverse Nuclear Spin Relaxation Studies of Viscoelastic Properties of Membrane Vesicles. I. Theory

Transverse nuclear spin relaxation measurements employing Carr-Purcell (CP) pulse sequences can provide detailed information on the slow-motional dynamics in biomembranes. In this paper, a comprehensive relaxation model is developed for the analysis of such experiments performed on unilamellar quasi-spherical vesicles. The basis of the model is the stochastic Liouville equation in which two different relaxation processes are considered (i.e., vesicle shape fluctuations and molecular translational diffusion). It is shown that for vesicle radii R 0 ≥ 200 nm, translational diffusion of the lipid molecules along the vesicle shell is too slow to contribute significantly to transverse spin relaxation in the kHz range, whereas vesicle shape fluctuations constitute the dominant transverse relaxation process. The theory is employed in model calculations for pulse frequency-dependent transverse 3 1 P nuclear spin relaxation rates. R C P 2 , ∞ (ω), from CP sequences. The analysis reveals that R C P 2 , ∞ (ω), induced by vesicle fluctuations, depends linearly on ω - 1 over a wide frequency range in the kHz regime. Notably, within this linear dispersion regime, the bending elastic modulus κ is the only relevant parameter because the magnitude of R C P 2 , ∞ (ω) does not depend on the size of the vesicle R 0 , the effective lateral tension σ, or the viscosity of the surrounding fluid η. On the other hand, R 0 , σ, ij, and K determine the frequency at which R C P 2 , ∞ (ω) levels off to a constant plateau value independent of ω. Thus, analysis of the R C P 2 , ∞ (ω) dispersion profiles is a direct way to determine the bending elastic modulus and other viscoelastic parameters of membrane vesicles.

Kinetics and mechanism of the addition of water and ring-opening of 2-methyl- and 2-aryl-4H-3,1-benzoxazines to 2-aminobenzyl esters in the acidic pH range; change in rate-limiting step with buffer concentration and evidence for a tetrahedral carbonyl addition intermediate

The observed rate coefficients for the reaction of 2-methyl-, 2-phenyl- and 2-(4-nitrophenyl)-4H-3,1-benzoxazines to give the corresponding 2-aminobenzyl esters increase as the pH is lowered and reach a constant plateau value at pH 2–4 depending on the substituent. The plateau region corresponds to complete conversion of the benzoxazine to the protonated benzoxazine (SH+) which is the reactive species. Values of pKSH+ calculated by fitting the appropriate rate expression to the rate–pH profile and the pKSH+ values measured spectrophotometrically before significant reaction to the ester has taken place are in good agreement. For each benzoxazine the observed rate coefficients show a rectilinear dependence on buffer concentration. A mechanism is proposed involving addition of water to the protonated benzoxazine to give a cyclic tetrahedral carbonyl addition intermediate. At low buffer concentrations, buffer catalysed collapse of the intermediate to product is rate-limiting and the reaction is first order in buffer. At high buffer concentrations, collapse of the intermediate to product is rapid and addition of water to the protonated benzoxazine to give the intermediate is rate-limiting.

Inactivation of batrachotoxin-modified Na+ channels in GH3 cells. Characterization and pharmacological modification.

Batrachotoxin (BTX)-modified Na+ currents were characterized in GH3 cells with a reversed Na+ gradient under whole-cell voltage clamp conditions. BTX shifts the threshold of Na+ channel activation by approximately 40 mV in the hyperpolarizing direction and nearly eliminates the declining phase of Na+ currents at all voltages, suggesting that Na+ channel inactivation is removed. Paradoxically, the steady-state inactivation (h infinity) of BTX-modified Na+ channels as determined by a two-pulse protocol shows that inactivation is still present and occurs maximally near -70 mV. About 45% of BTX-modified Na+ channels are inactivated at this voltage. The development of inactivation follows a sum of two exponential functions with tau d(fast) = 10 ms and tau d(slow) = 125 ms at -70 mV. Recovery from inactivation can be achieved after hyperpolarizing the membrane to voltages more negative than -120 mV. The time course of recovery is best described by a sum of two exponentials with tau r(fast) = 6.0 ms and tau r(slow) = 240 ms at -170 mV. After reaching a minimum at -70 mV, the h infinity curve of BTX-modified Na+ channels turns upward to reach a constant plateau value of approximately 0.9 at voltages above 0 mV. Evidently, the inactivated, BTX-modified Na+ channels can be forced open at more positive potentials. The reopening kinetics of the inactivated channels follows a single exponential with a time constant of 160 ms at +50 mV. Both chloramine-T (at 0.5 mM) and alpha-scorpion toxin (at 200 nM) diminish the inactivation of BTX-modified Na+ channels. In contrast, benzocaine at 1 mM drastically enhances the inactivation of BTX-modified Na+ channels. The h infinity curve reaches minimum of less than 0.1 at -70 mV, indicating that benzocaine binds preferentially with inactivated, BTX-modified Na+ channels. Together, these results imply that BTX-modified Na+ channels are governed by an inactivation process.

Mechanisms for the sputtering of rare gas solids by keV ions

Measurements have been made of the total sputtering yield and the corresponding energy spectra of ejected particles for several 30 keV ions incident on Ar, Kr, and Xe targets. This information is used to construct absolute yield curves that are differential in ejection energy for comparison with corresponding curves obtained from collision cascade theory. The ejection rate from the surface is found to depend on ion fluence, falling from a high initial value to a constant plateau value. The results indicate that for incident Ne + on Kr and Xe good agreement between experiment and theory can be obtained on a comparison of total yields if the plateau values are used, but that a comparison on the basis of the differential yield curves at high ejection energies indicates that better agreement is obtained by using the initial instantaneous yield values.

Dynamic light‐scattering studies of internal motions in DNA. I. Applicability of the rouse‐zimm model

AbstractThe intermediate scattering function G(K,t) for any polymer model obeying a linear separable Langevin equation can be expressed in terms of the eigenvalues and eigenvectors of its normal coordinate transformation. An algorithm for the extract numerical evaluation of G(K,t) for linear Rouse‐Zimm chains in the presence of hydrodynamic interaction has been developed. The computed G(K,t)2 were fit to C(t) = A exp(−t/τA) + B, and apparent diffusion coefficients calculated according to Dapp ≡ 1/(2τAK2). G(K,t)2 was surprisingly well‐fit by single‐exponential decays, especially at both small and large values of Kb, where K is the scattering vector and b the root‐mean‐squared subunit extension. Plots of Dapp vs K2 in‐variably showed a sigmoidal rise from D0 at K2 = O up to a constant plateau value at large K2b2.Analytical expression for G(K,t), exact in the limit of short times, were obtained for circular Rouse‐Zimm chains with and without hydrodynamic interaction, and also for free‐draining linear chains, and in addition for the independent‐segment‐mean‐force (ISMF) model. The predicted behaviors for G(K,t) at large Kb (or KRG) was found in all cases to be single‐exponential with 1/τ ∝ K2 at large Kb, in agreement with the computational results. A simple procedure for estamating all parameter of the Rouse‐Zimm model from a plot of Dapp vs K2 is proposed.Experimental data for both native and pH‐denatured calf‐thymus DNA in 1.0M Nacl with and without EDTA clearly plateau behavior of Dapp at large values of K, in harmony with the present Rouse‐Zimm and ISMF theories, and in sharp contrast to previous predictions based on the Rouse‐Zimm model.

Electrophoresis in Highly Cross-linked Polyacrylamide Gels

Abstract The properties of polyacrylamide gels with 1 to 50% cross-linking (%C) were studied using electrophoresis in multiphasic buffer systems of five proteins with known molecular weight. The extrapolated free mobility (Y 0 or M 0 varies in a biphasic manner with %C, reaching a maximum when %C is 5 to 7%, and falling to a constant plateau value specific for each protein when %C is greater than 20%. The retardation coefficient (KR ) shows a different type of biphasic relationship with %C: it increases with %C over the range 1-5%C and then falls asymptotically to zero, irrespective of molecular size. High %C provides a substantial increase in the effective pore size of the gel and enables one to fractionate macromolecules in the multimillion molecular weight range. These gels should be useful when it is desired to minimize molecular sieving, e.g., for isotachophoresis and isoelectric focusing.