Dislocation Formation and Work-Hardening in Two-Phase Alloys

A phase field model is presented to investigate dislocation formation (coherency loss) and workhardening in two-phase binary alloys. In our model the elastic energy density is a periodic function of the shear and tetragonal strains, which allows multiple formation of slips (dislocation dipoles). By numerically integrating the dynamic equations in two dimensions, we find that dislocations appear in pairs in the interface region and grow into slips. One end of each slip glides preferentially into the softer region, while the other end remains trapped at the interface. Under uniaxial stretching at deep quenching, slips appear in the softer regions and do not penetrate into the harder domains, giving rise to an increase of the stress with increasing applied strain in plastic flow.Comment: 14 figures (Higher resolution figures can be obtained at http://stat.scphys.kyoto-u.ac.jp/~minami_a/pict/cond-mat0405177/

Phase transition in compressible Ising systems at fixed volume

Using a Ginzburg-Landau model, we study the phase transition behavior of compressible Ising systems at constant volume by varying the temperature $T$ and the applied magnetic field $h$. We show that two phases can coexist macroscopically in equilibrium within a closed region in the $T$-$h$ plane. It occurence is favored near tricriticality. We find a field-induced critical point, where the correlation length diverges, the difference of the coexisting two phases and the surface tension vanish, but the isothermal magnetic susceptibility does not diverge in the mean field theory. We also investigate phase ordering numerically.Comment: 13 figure

Study of the factors related to atrial fibrillation after coronary artery bypass grafting: A search for a marker to predict the occurrence of atrial fibrillation before surgical intervention

ObjectiveAtrial fibrillation after cardiac surgery is a frequent complication. In this study we studied various factors in addition to trying to identify a marker that would predict the potential for atrial fibrillation before surgical intervention to prevent its occurrence.MethodsWe targeted 234 cases in which isolated coronary artery bypass grafting had been performed. The items for study included age, EuroSCORE, and maximum values of creatine phosphokinase–MB, troponin I, and angiotensin II after surgical intervention and preoperative values of atrial natriuretic peptide, brain natriuretic peptide, and C-reactive protein. As fibrotic markers, we measured levels of the sialylated carbohydrate antigen KL-6 in the blood, hyaluronic acid, and pyridinoline cross-linked carboxyterminal telepeptide of type I collagen C. At the time of surgical intervention, a section of the right atrium was extracted, and atrial natriuretic peptide, the sialylated carbohydrate antigen KL-6, hyaluronic acid, and pyridinoline cross-linked telopeptide of type I collagen levels were measured.ResultsAtrial fibrillation was observed in 73 (31.2%) cases, and preoperative factors that showed statistically significant differences in the occurrence of atrial fibrillation included age, EuroSCORE, and preoperative values of atrial natriuretic peptide, angiotensin II, the sialylated carbohydrate antigen KL-6, hyaluronic acid, and pyridinoline cross-linked telopeptide of type I collagen in the blood. As for intraoperative and postoperative factors, statistically significant differences were observed in the postoperative maximum of angiotensin II, atrial natriuretic peptide of the right atrium, the sialylated carbohydrate antigen KL-6, hyaluronic acid, and pyridinoline cross-linked telopeptide of type I collagen levels.ConclusionThe fibrosis of tissue associated with age is believed to be closely related to the occurrence of atrial fibrillation after coronary artery bypass grafting. This study suggests that the preoperative values of atrial natriuretic peptide, angiotensin II, the sialylated carbohydrate antigen KL-6, hyaluronic acid, and pyridinoline cross-linked telopeptide of type I collagen in the blood are useful as a new index for the occurrence of atrial fibrillation after coronary artery bypass grafting

A bacterial platform for fermentative production of plant alkaloids

The secondary metabolites of higher plants include diverse chemicals, such as alkaloids, isoprenoids and phenolic compounds (phenylpropanoids and flavonoids). Although these compounds are widely used in human health and nutrition, at present they are mainly obtained by extraction from plants and extraction yields are low because most of these metabolites accumulate at low levels in plant cells. Recent advances in synthetic biology and metabolic engineering have enabled tailored production of plant secondary metabolites in microorganisms, but these methods often require the addition of expensive substrates. Here we develop an Escherichia coli fermentation system that yields plant alkaloids from simple carbon sources, using selected enzymes to construct a tailor-made biosynthetic pathway. In this system, engineered cells cultured in growth medium without additional substrates produce the plant benzylisoquinoline alkaloid, (S)-reticuline (yield, 46.0 mg l−1 culture medium). The fermentation platform described here offers opportunities for low-cost production of many diverse alkaloids

Sheared Solid Materials

We present a time-dependent Ginzburg-Landau model of nonlinear elasticity in solid materials. We assume that the elastic energy density is a periodic function of the shear and tetragonal strains owing to the underlying lattice structure. With this new ingredient, solving the equations yields formation of dislocation dipoles or slips. In plastic flow high-density dislocations emerge at large strains to accumulate and grow into shear bands where the strains are localized. In addition to the elastic displacement, we also introduce the local free volume {\it m}. For very small $m$ the defect structures are metastable and long-lived where the dislocations are pinned by the Peierls potential barrier. However, if the shear modulus decreases with increasing {\it m}, accumulation of {\it m} around dislocation cores eventually breaks the Peierls potential leading to slow relaxations in the stress and the free energy (aging). As another application of our scheme, we also study dislocation formation in two-phase alloys (coherency loss) under shear strains, where dislocations glide preferentially in the softer regions and are trapped at the interfaces.Comment: 16pages, 11figure

Comorbid depressive disorders and left-side dominant occlusal discomfort in patients with phantom bite syndrome

Background: Phantom bite syndrome (PBS) is characterised by occlusal discomfort without corresponding dental abnormalities. Despite repeated, failed dental treatments, patients with PBS persist in seeking bite correction. PBS has been regarded as a mental disorder. However, we have reported that PBS patients with a dental trigger tend to have less psychiatric history than those without. Hence, the symptoms of PBS cannot be explained by a mental disorder alone, and it is unclear if mental disorders affect occlusal sensation. Objective: To elucidate the pathophysiology of PBS, we analysed the dental history, PBS symptom laterality and psychiatric history of patients. Methods: In this retrospective study, we reviewed outpatients with PBS who presented at our clinic between April 2012 and March 2017. Their medical records were reviewed for demographic data, medical history and laterality of occlusal discomfort. Results: Approximately half of the 199 enrolled patients had bilateral occlusal discomfort. In the others, the side with occlusal discomfort generally tended to be the one that had received dental treatment. There was no significant relationship between the side chiefly affected by occlusal discomfort and whether dental treatment had been received; however, the affected side differed depending on whether the patient had comorbid psychiatric disorders (P = .041). Conclusions: The distributions of the side with symptoms of PBS were different between those with and without comorbid psychiatric disorders, suggesting that psychiatric disorders might affect occlusal sensation due to a subtle dysfunction in brain areas central to sensory integration. Central dysfunction might play an important role in PBS