Explore the vast range of titles available.

The flow and deformation of macromolecules is ubiquitous in nature and industry, and an understanding of this phenomenon at both macroscopic and microscopic length scales is of fundamental and practical importance. Here, we present the formulation of a general mathematical framework, which could be used to extract, from scattering experiments, the molecular relaxation of deformed polymers. By combining and modestly extending several key conceptual ingredients in the literature, we show how the anisotropic single-chain structure factor can be decomposed by spherical harmonics and experimentally reconstructed from its cross sections on the scattering planes. The resulting wave-number-dependent expansion coefficients constitute a characteristic fingerprint of the macromolecular deformation, permitting detailed examinations of polymer dynamics at the microscopic level. We apply this approach to survey a long-standing problem in polymer physics regarding the molecular relaxation in entangled polymers after a large step deformation. The classical tube theory of Doi and Edwards predicts a fast chain retraction process immediately after the deformation, followed by a slow orientation relaxation through the reptation mechanism. This chain retraction hypothesis, which is the keystone of the tube theory for macromolecular flow and deformation, is critically examined by analyzing the fine features of the two-dimensional anisotropic spectra from small-angle neutron scattering by entangled polystyrenes. We show that the unique scattering patterns associated with the chain retraction mechanism are not experimentally observed. This result calls for a fundamental revision of the current theoretical picture for nonlinear rheological behavior of entangled polymeric liquids.

To evaluate the performance of the Prostate Health Index (PHI) in magnetic resonance imaging-transrectal ultrasound (MRI-TRUS) fusion prostate biopsy for the detection of clinically significant prostate cancer (csPCa). We prospectively enrolled 164 patients with at least one Prostate Imaging Reporting and Data System version 2 (PI-RADS v2) ≥ 3 lesions who underwent MRI-TRUS fusion prostate biopsy. Of the PSA-derived biomarkers, the PHI had the best performance in predicting csPCa (AUC 0.792, CI 0.707–0.877) in patients with PI-RADS 4/5 lesions. Furthermore, the predictive power of PHI was even higher in the patients with PI-RADS 3 lesions (AUC 0.884, CI 0.792–0.976). To minimize missing csPCa, we used a PHI cutoff of 27 and 7.4% of patients with PI-RADS 4/5 lesions could have avoided a biopsy. At this level, 2.0% of cases with csPCa would have been missed, with sensitivity and NPV rates of 98.0% and 87.5%, respectively. However, the subgroup of PI-RADS 3 was too small to define the optimal PHI cutoff. PHI was the best PSA-derived biomarker to predict csPCa in MRI-TRUS fusion prostate biopsies in men with PI-RADS ≥ 3 lesions, especially for the patients with PI-RADS 3 lesions who gained the most value.

We propose a microscopic picture for understanding the nonlinear rheology of supercooled liquids with soft repulsive potentials. Based on Brownian dynamics simulations of supercooled charge-stabilized colloidal suspensions, our analysis shows that the shear thinning of viscosity (η) at large enough shear rates (γ˙), expressed asη∼γ˙−λ, originates from the evolution of the localized elastic region (LER). An LER is a transient zone composed of the first several coordination shells of a reference particle. In response to the external shear, particles within the LER undergo nearly affine displacement before the yielding of the LER. The characteristic strain (γ) and size (ξ) of the LER, respectively, depend on the shear rate byγ∼γ˙εandξ∼γ˙−ν. Three exponents,λ,ε, andν, are related byλ=1−ε=4ν. This simple relation connects the nonlinear rheology to the elastic properties and the microscopic configurational distortion of the system. The relaxation of the LER is promoted by the large-step nonaffine particle displacement along the extensional direction of the shear geometry with the step length of 0.4 particle diameter. The elastic deformation and relaxation of the LER are ubiquitous and successive in the flow, which compose the fundamental process governing the bulk nonlinear viscoelasticity. We apply this model to analyze the rheo-small-angle neutron scattering data of sheared charge-stabilized colloidal suspensions. It is seen that our model well explains the neutron spectra and the rheological data.

Background/Aims: Melatonin has been demonstrated to protect cardiac microvascular endothelial cells (CMECs) against ischemia/reperfusion injury (IRI). Autophagy plays different roles in the heart during ischemia and reperfusion. The AMP activated protein kinase/mammalian target of rapamycin (AMPK/mTOR) pathway is associated with autophagy. This study sought to explore whether melatonin regulates CMEC autophagy through the AMPK/mTOR signaling pathway. Methods: The effects of melatonin in IRI were investigated in vivo rat models and in vitro neonatal CMECs. Myocardial infarct size was achieved by Evans blue and triphenyltetrazolium chloride staining. The severity of cell injury was evaluated by cell vitality and lactate dehydrogenase (LDH) release assays, and autophagy was evaluated by transmission electron microscopy and the assessment of autophagy-related gene expression, such as that of Beclin 1 and light chain 3-II. Results: In vivo, melatonin markedly reduced infarcted area, improved cardiac function and decreased LDH release. However, the AMPK activator AICAR and the mTOR inhibitor rapamycin reduced the protective effects of melatonin on IRI. In vitro, Beclin1 and light chain 3-II protein were found to be down-regulated and autophagosomes were found to be reduced in response to melatonin, together with an increase in cell vitality and a decrease in LDH. Treatment with AICAR or rapamycin ablated the benefit observed with melatonin treatment. Conclusions: Melatonin played an important and protective role in CMECs by inhibiting autophagy against IRI via the AMPK/mTOR system.

Green’s function for a two-dimensional anisotropic elastic solid containing a rigid or elastic inclusion has been previously explored. According to the special feature of Stroh formalism for two-dimensional anisotropic elasticity, the same mathematical form of Green’s function can be extended to cases with piezoelectric and magneto-electro-elastic materials by expanding the related matrix dimension. In this paper, we show that some important constant terms are missing in the existing Green’s functions and the solutions should be corrected to ensure the displacement and traction continuity across the inclusion interface. Besides the necessary analytical check, a further verification is provided by applying the corrected Green’s functions to the problems of crack-inclusion interaction. We consider that the cracks exist in smart materials made by composites embedded with piezoelectric and/or magneto-electro-elastic sensors and actuators. Since the anisotropic elastic, piezoelectric and magneto-electro-elastic materials exist simultaneously, an adaptable adjustment technique is proposed. With this technique, the dislocation superposition method and boundary-based finite element methods developed previously for the problems with a single material type can now be extended to study the coupled-field interaction problems.

The fabrication and characterization of a magnetic micro sensor (MMS) with two magnetic field effect transistors (MAGFETs) based on the commercial complementary metal oxide semiconductor (CMOS) process are investigated. The magnetic micro sensor is a three-axis sensing type. The structure of the magnetic microsensor is composed of an x/y-MAGFET and a z-MAGFET. The x/y-MAGFET is employed to sense the magnetic field (MF) in the x- and y-axis, and the z-MAGFET is used to detect the MF in the z-axis. To increase the sensitivity of the magnetic microsensor, gates are introduced into the two MAGFETs. The sensing current of the MAGFET enhances when a bias voltage is applied to the gates. The finite element method software Sentaurus TCAD was used to analyze the MMS’s performance. Experiments show that the MMS has a sensitivity of 182 mV/T in the x-axis MF and a sensitivity of 180 mV/T in the y-axis MF. The sensitivity of the MMS is 27.8 mV/T in the z-axis MF.

Small angle scattering techniques have now been routinely used to quantitatively determine the potential of mean force in colloidal suspensions. However the numerical accuracy of data interpretation is often compounded by the approximations adopted by liquid state analytical theories. To circumvent this long standing issue, here we outline a machine learning strategy for determining the effective interaction in the condensed phases of matter using scattering. Via a case study of colloidal suspensions, we show that the effective potential can be probabilistically inferred from the scattering spectra without any restriction imposed by model assumptions. Comparisons to existing parametric approaches demonstrate the superior performance of this method in accuracy, efficiency, and applicability. This method can effectively enable quantification of interaction in highly correlated systems using scattering and diffraction experiments. Gels, foams, and paints fall into a class of soft matter materials with widespread usage in modern technologies. This paper combines machine learning and spectral analysis techniques to develop a toolbox to model the complex interactions in this family of materials, which allows to quantitatively extract the system parameters from data.

Angelica sinensis (AS), one of the most versatile herbal medicines remains widely used due to its multi-faceted pharmacologic activities. Besides its traditional use as the blood-nourishing tonic, its anti-hypertensive, anti-cardiovascular, neuroprotective and anti-cancer effects have been reported. Albeit the significant therapeutic effects, how AS exerts such diverse efficacies from the molecular level remains elusive. Here we investigate the influences of AS and four representative phthalide derivatives from AS on the structure and function of hemoglobin (Hb). From the spectroscopy and oxygen equilibrium experiments, we show that AS and the chosen phthalides inhibited the oxygenated Hb from transforming into the high-affinity “relaxed” (R) state, decreasing Hb’s oxygen affinity. It reveals that phthalides cooperate with the endogenous Hb modulator, 2,3-bisphosphoglycerate (2,3-BPG) to synergetically regulate Hb allostery. From the docking modeling, phthalides appear to interact with Hb mainly through its α 1 /α 2 interface, likely strengthening four (out of six) Hb “tense” (T) state stabilizing salt-bridges. A new allosteric-modulating mechanism is proposed to rationalize the capacity of phthalides to facilitate Hb oxygen transport, which may be inherently correlated with the therapeutic activities of AS. The potential of phthalides to serve as 2,3-BPG substitutes/supplements and their implications in the systemic biology and preventive medicine are discussed.

Purpose This paper aims to establish the predictive equations of height, area and volume of printed solder paste during solder paste stencil printing (SPSP) process in surface mount technology (SMT) to better understand the effect of process parameters on the printing quality. Design/methodology/approach An experiment plan is proposed based on the response surface method (RSM). Experiments with 30 different combinations of process parameters are performed using a solder paste printer. After printing, the volume, area and height of the printed SAC105 solder paste are measured by a solder paste inspection machine. Using RSM, the predictive equations associated with the printing parameters and the printing quality of the solder paste are formed. Findings The optimal printing parameters are 175.08 N printing pressure, 250 mm/s printing speed, 0.1 mm snap-off height and 15.7 mm/s stencil snap-off speed if the target height of solder paste is 100 µm. As the target printing area of solder paste is 1.1 mm × 1.3 mm, the optimized values of the printing parameters are 140.29 N, 100.52 mm/s, 0.63 mm and 20.25 mm/s. When both the target printing height and area are optimized together, the optimal values for the four parameters are 86.67 N, 225.76 mm/s, 0.15 mm and 1.82 mm/s. Originality/value A simple RSM-based experimental method is proposed to formulate the predictive polynomial equations for height, area and volume of printed solder paste in terms of important SPSP parameters. The predictive equation model can be applied to the actual SPSP process, allowing engineers to quickly predict the best printing parameters during parameter setting to improve production efficiency and quality.

We report on the rheology of isotropic and nematic aqueous solutions of a sulfonated all-aromatic polyamide, poly(2,2′-disulfonyl-4,4′-benzidine terephthalamide) (PBDT), that forms high-aspect-ratio rod-like assemblies. For quiescently isotropic solutions, the concentration dependence of the zero-shear viscosity, longest relaxation time, and terminal modulus shows deviations in comparison to the Doi-Edwards theory for hard rods. For quiescently nematic solutions, we characterize the flow behavior through steady-state and transient nonlinear rheological measurements in conjunction with small-angle neutron scattering under shear. The steady-state flow curve is characterized by two anomalous shear thickening responses, one at moderate shear rates and the other immediately prior to flow alignment at high shear rates. We assign the origin of these shear thickening response to director “kayaking” and “out-of-plane steady” states, using predictions from prior high-resolution numerical simulations of sheared nematic rods. Utilizing transient shear flow reversals and step-down experiments, we characterize the oscillatory response of the nematic director through these flow regimes. When the first normal stress difference is plotted versus the shear stress during a transient step-down, the so-called dynamic stress path, the counterclockwise versus clockwise rotation has previously been shown to reveal the relative dominance of viscous versus elastic contributions to the stress tensor, respectively. Our measurements strongly suggest that the anomalous shear thickening behavior in nematic PBDT solutions arises from viscous stresses developed as the ensemble of rods undergoes periodic oscillatory motion under shear, rather than elastic stresses due to broadening of the orientational distribution function.