Critical role of lattice vacancies in pressure-induced phase transitions of baroplastic diblock copolymers.

Baroplastic diblock copolymers exhibit order-disorder transitions and melt upon compression at low temperatures, in some cases even at ambient temperatures. Their unique low-temperature processability makes them promising candidates for sustainable polymeric materials. Despite their potential, however, the molecular mechanisms governing the pressure-induced phase transitions of these copolymers remain largely unexplored.

Comparison of gels synthesized by controlled radical copolymerization and free radical copolymerization: molecular dynamics simulation.

The structures of gels synthesized by controlled radical copolymerization (CRP) and conventional free radical copolymerization (FRP) were studied by a coarse-grained molecular dynamics simulation. It was confirmed that the CRP gel has a larger number of elastically effective chains and fewer cyclic structures and entanglements than the FRP gel, , the network structure of the CRP gel is more uniform than that of the FRP gel. However, the difference in the shear modulus between the two gels was small due to the opposing changes in the number of elastically effective chains and that of entanglements.

Engine performance and emissions evaluation of surfactant-free B30 biodiesel-diesel/water emulsion as alternative fuel.

Malaysia is one of the top exporters of palm oil, and although currently facing fierce resistance towards palm oil imports in some parts of the globe, one of the ways to utilize this commodity is by increasing palm biodiesel content in local commercial diesel. However, due to the oxygen-rich nature of biodiesel, its utilization suffers from increased nitrogen oxides (NO) emission compared to conventional diesel. To mitigate this issue and improve diesel engine performance and emissions using biodiesel-diesel blends, this study attempted to investigate implementation of a real-time non-surfactant emulsion fuel supply system (RTES) which produces water-in-diesel emulsion as fuel without surfactants.

Deep-Sea-Inspired Chemistry: A Hitchhiker's Guide to the Bottom of the Ocean for Chemists.

The ocean constitutes approximately 70% of Earth's surface. Its average depth is 3688 m, of which depths beyond 200 m are classified as the deep sea. The deep sea is distinct from the surface of the ocean in terms of pressure, temperature, and sunlight.

Molecular Simulation and Theoretical Analysis of Slide-Ring Gels under Biaxial Deformation.

Slide-ring (SR) gels, a new type of gels that have cross-links moving along the chains, are known to have unique mechanical characteristics. In the case of biaxial deformations, it has been experimentally shown that the stress-strain (S-S) relationships of SR gels can be well described by the neo-Hookean (NH) model. This behavior is quite different from that of conventional chemical gels, where the S-S curves deviate from the NH model.

Relationship between nutrition and reproduction.

Background: Recently, the relationship between nutrition and reproduction is being studied. In particular, when older women receive reproductive treatment, egg aging causes greater problems than organic factors.

Methods: This study investigated the relationship between nutrition and reproduction with a focus on factors that cause aging, including oxidation, glycation, and chronic inflammation.

Theory of transient networks with a well-defined junction structure.

The present study constructs a theory of physical gels consisting of bifunctional molecules, f-functional molecules, and solvent. This theory considered the formation of loops (i.e.

Molecular simulation of structures and mechanical properties of nanocomposite networks consisting of disk-shaped particles and polymers.

We study the structures and the mechanical properties of nanocomposite networks consisting of disk-shaped particles and polymers by a coarse-grained molecular dynamics simulation. The disk-shaped particles and the polymers form tightly cross-linked network structures by the polymer adsorption on the disk-shaped particles and show high mechanical strength. We confirm the significance of the high polymerization degree for the large fracture elongations.

Theoretical Analysis of Critical Flowable Physical Gel Cross-Linked by Metal Ions and Polyacrylamide-Derivative Associating Polymers Containing Imidazole Groups.

When the polymer chains are cross-linked by physical bonds having a finite lifetime, the relaxation time and viscosity do not diverge at the gel point though percolation occurs. These undivergent quantities are related to the finite-sized "largest relaxed cluster," which can relax before it breaks. Its size is the key rheological parameter characterizing of the critical physical gels.

Theoretical Study of Network Formation and Mechanical Properties of Physical Gels with a Well-Defined Junction Structure.

A statistical-mechanical theory of thermoreversible gelation considering loops for the system consisting of bifunctional polymer units carrying A functional groups and trifunctional units carrying B functional groups at their ends is constructed. We obtain the sol-gel transition line and the properties of the post-gel region as functions of the polymer concentration, temperature, association constant, and loop parameter using the present theory. In this article, we calculate the number concentration of elastically effective chains in the gel region and obtain the shear modulus by an application of the phantom network theory.

Exclusion of impurity particles during grain growth in charged colloidal crystals.

We examine the spatial distribution of fluorescent-labeled charged polystyrene (PS) particles (particle volume fraction ϕ = 0.0001 and 0.001, diameter d = 183 and 333 nm) added to colloidal crystals of charged silica particles (ϕ = ϕ(s) = 0.

Hydration, phase separation and nonlinear rheology of temperature-sensitive water-soluble polymers.

The collapse of a poly(N-isopropylacrylamide) (PNIPAM) chain upon heating and the phase diagrams of aqueous PNIPAM solutions with a very flat lower critical solution temperature (LCST) phase separation line are theoretically studied on the basis of cooperative dehydration (simultaneous dissociation of bound water molecules in a group of correlated sequence), and compared with the experimental observation of temperature-induced coil-globule transition by light scattering methods. The transition becomes sharper with the cooperativity parameter σ of hydration. The reentrant coil-globule-coil transition and cononsolvency in a mixed solvent of water and methanol are also studied from the viewpoint of competitive hydrogen bonds between polymer-water and polymer-methanol.

Stress buildup under start-up shear flows in self-assembled transient networks of telechelic associating polymers.

The nonaffine transient network theory is used to study the time development of the shear and normal stresses under start-up shear flows in networks formed by self-assembled telechelic, hydrophobically modified water-soluble polymers. The initial slope, strain hardening, and overshoot of the shear stress are studied in detail in relation to the nonlinear tension-elongation curve of the elastically active chains in the network. The condition for the occurrence of strain hardening (upward deviation of the stress from the reference curve defined by the linear moduli) is found to be gamma > gammac(A), where gamma is the shear rate, gamma(c) is its critical value for strain hardening, and A is the amplitude of the nonlinear term in the tension of a chain.

Temperature-responsive polymers in mixed solvents: competitive hydrogen bonds cause cononsolvency.

If two good solvents become poor for a polymer when mixed, the solvent pair is called a cononsolvent pair. The sharp reentrant coil-to-globule-to-coil transition of a poly(N-isopropylacrylamide) chain observed in the mixed solvent of water and methanol is shown to be caused by the competitive hydrogen bonding by water and methanol molecules onto the polymer chain. On the basis of a new statistical-mechanical model for competitive hydrogen bonds, the mean square end-to-end distance is theoretically calculated and compared with experiment.

Fetal aortic distension waveforms for evaluating cardiac function and changes in blood pressure: fetal lamb validation.

Aim: To investigate which part of the fetal aortic distension waveform is mainly influenced by changes in fetal cardiac contractility and aortic blood pressure.

Methods: In acute preparation, aortic distension waveforms were recorded using an echo-tracking system, and aortic and left ventricular pressure waveforms were obtained from six late-gestation catheterized fetal lambs. Dobutamine and angiotensin II were separately infused and the correlations between the maximum value in the first derivative of left ventricle pressure waveforms (Max dP/dt) and fetal blood pressure, and the parameters obtained from aortic distension waveforms were analyzed using linear regression analysis.

Multicanonical Monte Carlo simulations on intramolecular micelle formation in copolymers.

The formation of intramolecular micelles in copolymers with periodic sequence, where hydrophobic units (stickers) are periodically placed along the chain, is studied by using multicanonical Monte Carlo computer simulations for an off-lattice bead-rod model in three dimensions. With decreasing the temperature, a transition from random-coil conformations to micelles occurs and flower-type micelles are formed via the transition. The number of stickers forming a micelle core is limited by the excluded-volume effect of loop chains around micelle cores.

Noninvasive measurement of isovolumetric contraction time during hypoxemia and acidemia: Fetal lamb validation as an index of cardiac contractility.

Objectives: The objectives of this study are firstly to clarify how the Doppler isovolumetric contraction time (ICT) is influenced by arterial oxygen pressure (PaO2) or pH, and secondly to confirm the relationship between the Doppler ICT and myocardial contractility during hypoxemia and/or acidemia in the fetal lamb.

Material And Methods: In 12 pregnant ewes, fetal hypoxemia and acidemia were induced by giving ewes a variable mixture of gases for 120 min. The chronological change of fetal PaO2, pH, Doppler ICT and maximum first derivative of the left ventricular pressure waveform (Max dp/dt) was recorded every 30 min.

Prenatal diagnosis of slow-rate ventricular tachycardia using fetal electrocardiography.

Objectives: We report a case in which fetal ventricular tachycardia (VT) could be diagnosed, in utero, using a transabdominal fetal electrocardiogram (fECG) with motion-mode (M-mode) echocardiography.

Methods: The fetus was referred at 32 weeks' gestation due to tricuspid atresia. The fetal cardiotocogram demonstrated paroxysmal tachycardia with a ventricular rate of 155 to 160 bpm within the confines of normal sinus rhythm.

A new ultrasound technique to measure the isovolumetric contraction time as an index of cardiac contractility: fetal lamb validation.

Objective: We developed a noninvasive Doppler technique for measuring fetal cardiac isovolumetric contraction time (ICT). The purpose of this study was to determine how well our method reflects real cardiac performance using fetal lamb as an instrumented model.

Methods: The true ICT was measured by simultaneous recording of the pressure waves of the left ventricle and ascending aorta.

Aortic pulse waveforms for evaluating cardiac performance in the human fetus.

Pulse waveforms of the fetal descending aorta were obtained using an echo-tracking system to clarify the gestational age-related changes and the usefulness for detecting cardiac dysfunction. Peak systolic (PSD) and end diastolic diameter (EDD), pulse amplitude (Amp) and Amp:EDD ratio, calculated from the pulse waveforms, were adopted for analysis. In 196 normal fetuses after 20 weeks, the PSD, EDD and Amp increased, and Amp:EDD ratio decreased linearly with advancing gestation.