Nano-particle motion in monolithic silica column using single-particle tracking method

Porous materials are used in a variety of industrial applications owing to their large surface areas, large pore volumes, hierarchical porosities, and low densities. The motion of particles inside the pores of porous materials has attracted considerable attention. We investigated nano-particle motion in a porous material using the single-particle tracking method. Particle motion such as absorption and desorption at the wall was observed. The displacement probability distribution deviated from the Gaussian distribution at the tail, indicating non-Gaussian motion of the particles. Moreover, an analysis of the relative angle between three consecutive particle positions revealed that the probability of the particle moving backward was approximately twice that of the particle moving forward. These results indicate that particle motion inside porous materials is highly complex and that a single-particle study is essensital for fabricating a structure that is suitable for applications

Electroweak axion string and superconductivity

We study the axion strings with the electroweak gauge flux in the DFSZ axion model and show that these strings, called the electroweak axion strings, can exhibit superconductivity without fermionic zero modes. We construct three types of electroweak axion string solutions. Among them, the string with $W$-flux can be lightest in some parameter space, which leads to a stable superconducting cosmic string. We also show that a large electric current can flow along the string due to the Peccei-Quinn scale much higher than the electroweak scale. This large current induces a net attractive force between the axion strings with the same topological charge, which opens a novel possibility that the axion strings form Y-junctions in the early universe.Comment: 35 pages, 8 figures; v3: published versio

Two-Step Model of Fusion for Synthesis of Superheavy Elements

A new model is proposed for fusion mechanisms of massive nuclear systems where so-called fusion hindrance exists. The model describes two-body collision processes in an approaching phase and shape evolutions of an amalgamated system into the compound nucleus formation. It is applied to $^{48}$Ca-induced reactions and is found to reproduce the experimental fusion cross sections extremely well, without any free parameter. Combined with the statistical decay theory, residue cross sections for the superheavy elements can be readily calculated. Examples are given.Comment: 4 pages, 4 figure

Void-induced cross slip of screw dislocations in fcc copper

Pinning interaction between a screw dislocation and a void in fcc copper is investigated by means of molecular dynamics simulation. A screw dislocation bows out to undergo depinning on the original glide plane at low temperatures, where the behavior of the depinning stress is consistent with that obtained by a continuum model. If the temperature is higher than 300 K, the motion of a screw dislocation is no longer restricted to a single glide plane due to cross slip on the void surface. Several depinning mechanisms that involve multiple glide planes are found. In particular, a depinning mechanism that produces an intrinsic prismatic loop is found. We show that these complex depinning mechanisms significantly increase the depinning stress

Z-graded weak modules and regularity

It is proved that if any Z-graded weak module for vertex operator algebra V is completely reducible, then V is rational and C_2-cofinite. That is, V is regular. This gives a natural characterization of regular vertex operator algebras.Comment: 9 page

Production of four-quark states with double heavy quarks at LHC

We study the hadronic production of four-quark states with double heavy quarks and double light antiquarks at LHC. The production mechanism is that a color anti-triplet diquark cluster consisting of double heavy quarks is formed first from the produced double heavy quark-antiquark pairs via $gg$ fusion hard process, followed by the fragmentation of the diquark cluster into a four-quark (tetraquark) state. Predictions for the production cross sections and their differential distributions are presented. Our results show that it is quite promising to discover these tetraquark states in LHC experiments both for large number events and for their unique signatures in detectors.Comment: 17 pages,8 figure

Development of a new treatment for preterm birth complications using amniotic fluid stem cell therapy

This paper describes the current status of studies and clinical trials on the use of mesenchymal stem cells (MSCs) and amniotic fluid stem cells (AFSCs) for complications of preterm birth (PTB), an urgent issue in the perinatal field. PTB is a serious challenge in clinical medicine that is increasing globally, and effective control of its complications is necessary for newborns’ subsequent long life. Classical treatments are inadequate, and many patients have PTB complications. A growing body of evidence provided by translational medicine and others indicates that MSCs, and among them, the readily available AFSCs, may be useful in treating PTB complications. AFSCs are the only MSCs available prenatally and are known to be highly antiinflammatory and tissue-protective and do not form tumors when transplanted. Furthermore, because they are derived from the amniotic fluid, a medical waste product, no ethical issues are involved. AFSCs are an ideal cell resource for MSC therapy in neonates. This paper targets the brain, lungs, and intestines, which are the vital organs most likely to be damaged by PTB complications. The evidence to date and future prospects with MSCs and AFSCs for these organs are described

Quantum current dissipation in superconducting strings and vortons

In this work, the current stability is discussed for cosmic strings with the bosonic superconductivity. A non-vanishing curvature of string generally induce the quantum instability of the current-carrying particle. Its decay rates are explored for various types of model parameters, curved string shapes, and decay processes. As a cosmological application, the stability is examined for superconducting strings in the string network and also for cosmic vortons by evaluating their cosmological evolution. The zero mode and hence the vorton cannot be stable in various cases, e.g., with a hierarchy between the current-carrying particle mass off the string and the string tension or with sizable couplings of the current-carrying particle to light species such as the Standard Model particles.Comment: 42 pages, 14 figures, 1 tabl