A Unified Transformation Framework for Studying Various Situations of Vertical/Oblique Drop Impact on Horizontal/Inclined Stationary/Moving Flat Surfaces

There are various situations of drop impact on solid surfaces widely occurred in natural phenomenon or used in different industrial applications. However, comparing and classifying these drop impact situations is not easy due to different states of the parameters affecting drop impact dynamics. In this article, a unified transformation framework is proposed to study various situations of vertical/oblique drop impact on horizontal/inclined stationary/moving flat surfaces with/without a crossflow. This simple framework consists of a coordinate with normal and tangential axes on a horizontal stationary surface. For each drop impact situation, the drop velocity, gravitational acceleration, possible induced flow due to the moving surface, and possible crossflow are transformed into the framework. Comparing the transformed versions of considered drop impact situations facilitates identification of their physical similarities/differences and determines which situations (and under what conditions) lead to identical results and can be used interchangeably. Although common situations of drop impact on moving surfaces (having tangential component of surface velocity) lead to asymmetric drop spreading, the possibility of symmetric drop spreading on moving surfaces is demonstrated and analyzed using the proposed transformation framework. This interesting possibility means that for related production lines or experimental setups, where symmetrical drop spreading is required, the surface does not need to be stationary. In such applications/setups, the use of moving surfaces (rather than stationary surfaces) can considerably accelerate the symmetric drop impact process. Our simulation results of several of the considered drop impact situations well confirm the facilities/predictions of the proposed transformation framework

A new framework for characterization of poroelastic materials using indentation

To characterize a poroelastic material, typically an indenter is pressed onto the surface of the material with a ramp of a finite approach velocity followed by a hold where the indenter displacement is kept constant This leads to deformation of the porous matrix, pressurization of the interstitial fluid and relaxation due to redistribution of fluid through the pores. In most studies the poroelastic properties, including elastic modulus, Poisson ratio and poroelastic diffusion coefficient, are extracted by assuming an instantaneous step indentation. However, exerting step like indentation is not experimentally possible and usually a ramp indentation with a finite approach velocity is applied. Moreover, the poroelastic relaxation time highly depends on the approach velocity in addition to the poroelastic diffusion coefficient and the contact area. Here, we extensively studied the effect of indentation velocity using finite element simulations which has enabled the formulation of a new framework based on a master curve that incorporates the finite rise time. To verify our novel framework, the poroelastic properties of two types of hydrogels were extracted experimentally using indentation tests at both macro and micro scales. Our new framework that is based on consideration of finite approach velocity is experimentally easy to implement and provides more accurate estimation of poroelastic properties

Phase transition in Schwarzschild-de Sitter spacetime

Using a static massive spherically symmetric scalar field coupled to gravity in the Schwarzschild-de Sitter (SdS) background, first we consider some asymptotic solutions near horizon and their local equations of state(E.O.S) on them. We show that near cosmological and event horizons our scalar field behaves as a dust. At the next step near two pure de-Sitter or Schwarzschild horizons we obtain a coupling dependent pressure to energy density ratio. In the case of a minimally couplling this ratio is -1 which springs to the mind thermodynamical behavior of dark energy. If having a negative pressure behavior near these horizons we concluded that the coupling constant must be $\xi<{1/4}$ >. Therefore we derive a new constraint on the value of our coupling $\xi$ . These two different behaviors of unique matter in the distinct regions of spacetime at present era can be interpreted as a phase transition from dark matter to dark energy in the cosmic scales and construct a unified scenario.Comment: 7 pages,no figures,RevTex, Typos corrected and references adde

The MOSDEF survey: a stellar mass-SFR-metallicity relation exists at z∼2.3z\sim2.3

We investigate the nature of the relation among stellar mass, star-formation rate, and gas-phase metallicity (the M$_*$-SFR-Z relation) at high redshifts using a sample of 260 star-forming galaxies at $z\sim2.3$ from the MOSDEF survey. We present an analysis of the high-redshift M$_*$-SFR-Z relation based on several emission-line ratios for the first time. We show that a M$_*$-SFR-Z relation clearly exists at $z\sim2.3$. The strength of this relation is similar to predictions from cosmological hydrodynamical simulations. By performing a direct comparison of stacks of $z\sim0$ and $z\sim2.3$ galaxies, we find that $z\sim2.3$ galaxies have $\sim0.1$ dex lower metallicity at fixed M$_*$ and SFR. In the context of chemical evolution models, this evolution of the M$_*$-SFR-Z relation suggests an increase with redshift of the mass-loading factor at fixed M$_*$, as well as a decrease in the metallicity of infalling gas that is likely due to a lower importance of gas recycling relative to accretion from the intergalactic medium at high redshifts. Performing this analysis simultaneously with multiple metallicity-sensitive line ratios allows us to rule out the evolution in physical conditions (e.g., N/O ratio, ionization parameter, and hardness of the ionizing spectrum) at fixed metallicity as the source of the observed trends with redshift and with SFR at fixed M$_*$ at $z\sim2.3$. While this study highlights the promise of performing high-order tests of chemical evolution models at high redshifts, detailed quantitative comparisons ultimately await a full understanding of the evolution of metallicity calibrations with redshift.Comment: 19 pages, 8 figures, accepted to Ap

Salmonella enterica serovar Typhi lipopolysaccharide O-antigen modification impact on serum resistance and antibody recognition

Salmonella enterica serovar Typhi is a human-restricted Gram-negative bacterial pathogen responsible for causing an estimated 27 million cases of typhoid fever annually, leading to 217,000 deaths, and current vaccines do not offer full protection. The O-antigen side chain of the lipopolysaccharide is an immunodominant antigen, can define host-pathogen interactions, and is under consideration as a vaccine target for some Gram-negative species. The composition of the O-antigen can be modified by the activity of glycosyltransferase (gtr) operons acquired by horizontal gene transfer. Here we investigate the role of two gtr operons that we identified in the S. Typhi genome. Strains were engineered to express specific gtr operons. Full chemical analysis of the O-antigens of these strains identified gtr-dependent glucosylation and acetylation. The glucosylated form of the O-antigen mediated enhanced survival in human serum and decreased complement binding. A single nucleotide deviation from an epigenetic phase variation signature sequence rendered the expression of this glucosylating gtr operon uniform in the population. In contrast, the expression of the acetylating gtrC gene is controlled by epigenetic phase variation. Acetylation did not affect serum survival, but phase variation can be an immune evasion mechanism, and thus, this modification may contribute to persistence in a host. In murine immunization studies, both O-antigen modifications were generally immunodominant. Our results emphasize that natural O-antigen modifications should be taken into consideration when assessing responses to vaccines, especially O-antigen-based vaccines, and that the Salmonella gtr repertoire may confound the protective efficacy of broad-ranging Salmonella lipopolysaccharide conjugate vaccines

The MOSDEF Survey: Kinematic and Structural Evolution of Star-Forming Galaxies at 1.4≤z≤3.81.4\leq z\leq 3.8

We present ionized gas kinematics for 681 galaxies at $z\sim 1.4-3.8$ from the MOSFIRE Deep Evolution Field survey, measured using models which account for random galaxy-slit misalignments together with structural parameters derived from CANDELS Hubble Space Telescope (HST) imaging. Kinematics and sizes are used to derive dynamical masses. Baryonic masses are estimated from stellar masses and inferred gas masses from dust-corrected star formation rates (SFRs) and the Kennicutt-Schmidt relation. We measure resolved rotation for 105 galaxies. For the remaining 576 galaxies we use models based on HST imaging structural parameters together with integrated velocity dispersions and baryonic masses to statistically constrain the median ratio of intrinsic ordered to disordered motion, $V/\sigma_{V,0}$. We find that $V/\sigma_{V,0}$ increases with increasing stellar mass and decreasing specific SFR (sSFR). These trends may reflect marginal disk stability, where systems with higher gas fractions have thicker disks. For galaxies with detected rotation we assess trends between their kinematics and mass, sSFR, and baryon surface density ($\Sigma_{\mathrm{bar},e}$). Intrinsic dispersion correlates most with $\Sigma_{\mathrm{bar},e}$ and velocity correlates most with mass. By comparing dynamical and baryonic masses, we find that galaxies at $z\sim 1.4-3.8$ are baryon dominated within their effective radii ($R_E$), with Mdyn/Mbaryon increasing over time. The inferred baryon fractions within $R_E$, $f_{\mathrm{bar}}$, decrease over time, even at fixed mass, size, or surface density. At fixed redshift, $f_{\mathrm{bar}}$ does not appear to vary with stellar mass but increases with decreasing $R_E$ and increasing $\Sigma_{\mathrm{bar},e}$. For galaxies at $z\geq2$, the median inferred baryon fractions generally exceed 100%. We discuss possible explanations and future avenues to resolve this tension.Comment: Accepted to ApJ. Added Figure 9, corrected sample size (main results unchanged). 28 pages, 13 figure

Spinach consumption and nonalcoholic fatty liver disease among adults: a case�control study

Background: Spinach has high antioxidants and polyphenols and showed protective effects against liver diseases in experimental studies. We aimed to assess the association between dietary intake of spinach and odds of nonalcoholic fatty liver disease (NAFLD) in a case�control study among Iranian adults. Methods: Totally 225 newly diagnosed NAFLD patients and 450 controls, aged 20�60 years, were recruited in this study. Participants� dietary intakes were collected using a valid and reliable 168-item semi-quantitative food frequency questionnaire (FFQ). The logistic regression test was used for assessing the association between total, raw, and boiled dietary spinach with the odds of NAFLD. Results: The mean (SD) age and BMI of participants (53 male) were 38.1 (8.8) years and 26.8 (4.3) kg/m2, respectively. In the final adjusted model for potential confounders, the odds (95 CI) of NAFLD in individuals in the highest tertile of daily total and raw spinach intake was 0.36 (0.19�0.71), P_trend = 0.001 and 0.47 (0.24�0.89), P_trend = 0.008, respectively compared with those in the lowest tertile. Furthermore, in the adjusted analyses, an inverse association was observed between the highest yearly intake versus no raw spinach consumption and odds of NAFLD (OR 0.41; 95% CI 0.18�0.96), P for trend = 0.013. However, there was no significant association between higher boiled spinach intake and odds of NAFLD. Conclusions: The present study found an inverse association between total and raw spinach intake with the odds of NAFLD. © 2021, The Author(s)

Spherically symmetric vacuum solutions of modified gravity theory in higher dimensions

In this paper we investigate spherically symmetric vacuum solutions of $f(R)$ gravity in a higher dimensional spacetime. With this objective we construct a system of non-linear differential equations, whose solutions depend on the explicit form assumed for the function $F(R)=\frac{df(R)}{dR}$. We explicit show that for specific classes of this function exact solutions from the field equations are obtained; also we find approximated results for the metric tensor for more general cases admitting $F(R)$ close to the unity.Comment: 14 pages, no figure. New version accepted for publication in EPJ

Unexpectedly high pressure for molecular dissociation in liquid hydrogen by electronic simulation

The study of the high pressure phase diagram of hydrogen has continued with renewed effort for about one century as it remains a fundamental challenge for experimental and theoretical techniques. Here we employ an efficient molecular dynamics based on the quantum Monte Carlo method, which can describe accurately the electronic correlation and treat a large number of hydrogen atoms, allowing a realistic and reliable prediction of thermodynamic properties. We find that the molecular liquid phase is unexpectedly stable, and the transition towards a fully atomic liquid phase occurs at much higher pressure than previously believed. The old standing problem of low-temperature atomization is, therefore, still far from experimental reach

Non-vacuum Solutions of Bianchi Type VI_0 Universe in f(R) Gravity

In this paper, we solve the field equations in metric f(R) gravity for Bianchi type VI_0 spacetime and discuss evolution of the expanding universe. We find two types of non-vacuum solutions by taking isotropic and anisotropic fluids as the source of matter and dark energy. The physical behavior of these solutions is analyzed and compared in the future evolution with the help of some physical and geometrical parameters. It is concluded that in the presence of isotropic fluid, the model has singularity at $\tilde{t}=0$ and represents continuously expanding shearing universe currently entering into phantom phase. In anisotropic fluid, the model has no initial singularity and exhibits the uniform accelerating expansion. However, the spacetime does not achieve isotropy as $t\rightarrow\infty$ in both of these solutions.Comment: 20 pages, 5 figures, accepted for publication in Astrophys. Space Sc