Entanglement dynamics for static two-level atoms in cosmic string spacetime

We study the entanglement dynamics of two static atoms coupled with a bath of fluctuating scalar fields in vacuum in the cosmic string spacetime. Three different alignments of atoms, i.e. parallel, vertical, and symmetric alignments with respect to the cosmic string are considered. We focus on how entanglement degradation and generation are influenced by the cosmic string, and find that they are crucially dependent on the atom-string distance r, the interatomic separation L, and the parameter $$\nu$$ that characterizes the nontrivial topology of the cosmic string. For two atoms initially in a maximally entangled state, the destroyed entanglement can be revived when the atoms are aligned vertically to the string, which cannot happen in the Minkowski spacetime. When the symmetrically aligned two-atom system is initially in the antisymmetric state, the lifetime of entanglement can be significantly enhanced as $$\nu$$ increases. For two atoms which are initially in the excited state, when the interatomic separation is large compared to the transition wavelength, entanglement generation cannot happen in the Minkowski spacetime, while it can be achieved in the cosmic string spacetime when the position of the two atoms is appropriate with respect to the cosmic string and $$\nu$$ is large enough

Modelling and Analysis of Characteristics of a Piezoelectric-Actuated Micro-/Nano Compliant Platform Using Bond Graph Approach

The piezoelectric-actuated flexure-based compliant platform is commonly adopted in many fields of micro and nanotechnology. In this paper, bond graph modeling, and kinematic and dynamic characteristics of a piezoelectric-actuated micro-/nano compliant platform system are investigated. During modeling, the bond graph model of the piezoelectric actuator (PZT) is derived by considering both the electrical domain and the mechanical domain. Considering the compliances of flexure hinges and elastic linkages, as well as the input ends, the bond graph model for the bridge-type displacement amplification mechanism in the compliant platform is established by combining pseudo-rigid-body (PRB) model theory and elastic beam theory. Based on the interactions between the PZT subsystem and compliant platform subsystem, the kinematic performance of the proposed compliant platform system is evaluated through both computer simulations and experimental tests. Furthermore, the frequency responses, dynamic responses and load capacity of the compliant platform system are studied. This paper explores a new modeling method for a piezoelectric-actuated compliant platform system, which can provide an effective solution when analyzing the micro-/nano system

An experimental study on synthesis of β-Sialon composites using fly ash and lignite char-preparation and whiskers formation

β-Sialon based composites were produced using a vertical reactor by carbothermal reduction reaction under nitrogen using fly ash and lignite chars to examine the effects of mixing, carbon content, reaction temperature and sintering time. The influences of chars as a reductant were further investigated in comparison with graphite. The evolution of phase and morphology in samples were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). Mechanical stirring was favored to mix fly ash and chars, while ball-milling shove the chars with porous structure due to collisions of agate balls, preventing N₂ penetration to the inner parts of reactants. When excess carbon was increased to 100%, a higher combustion reactivity of low-temperature chars resulted in the production of SiC phase. The evolution of β-Sialon with increasing reaction temperature showed the samples mixed with chars were more sensitive to reaction temperature than that with graphite. β-Sialon phase increased gradually with increasing sintering time to 6 h and decreased thereafter due to the decomposition or conversion of β-Sialon. These changes were more significantly for samples adding lignite chars. The optimal operation has been determined and rod-like β-Sialon whiskers with high aspect ratio appeared after performing the operation. In the growth process of whiskers, bead-shape whiskers were observed, suggesting that the growth mechanism was different from the conventional vaporliquidsolid (VLS) mechanism

Rate of tendon gap closure in an in vitro collagen gel matrix

Tendon gap closure was examined in a tissue culture model and found to have a similar time course as skin wound closure . Foot tendons from White Rock chickens were mounted in a collagen gel matrix and maintained with the use of Dulbecco's modified Eagle medium, containing fetal calf serum and antibiotics, for 4 weeks at 37°C in an incubator . Gap distances between tendons were measured every 1 to 3 days and plotted against time as the contraction curve . After an initial lag period of 4 to 8 days, gap distance showed a progressive decrease, Gap closure rate was defined as the slope of the contraction curve, and it was found to be a function of initial gap distance (r = 0.643, p 0,045) . The time necessary to reduce the initial gap distance by half had a significant correlation with the initial gap distance (r = 0.986, p < 0.001). Fibroblast migration began on days 2 to 3 after a 1-to 2-day lag period . Fibroblasts were visible in the tendon gap region before the start of collagen gel contraction . At this time, the fibroblast migration rate was 0.33 mm/day . A critical density of fibroblasts was necessary to start collagen gel contraction. Once the gap distance began to diminish, fibroblast migration measurements were hampered because the measurable area was decreasing . Collagen gel contraction reduced the measurable fibroblast migration rate by nearly half to 0.18 mm/day . A linear correlation was found between fibroblast distance traveled and time in culture during both the gel lag and gel contraction time periods, This tendon culture model may be potentially useful for wound healing studies because it allows for studies of fibroblast activity in the early lag phase when the cells populate the collagen lattice but before contraction of the gel occurs . (WOUND REP REG 1997;5:62-8) Culturing fibroblasts in hydrated collagen gel lattices was introduced in 1972 by Elsdale and Bard' and expanded on in 1979 by Bell et al .2 as a technique for assessing fibroblast activity. These authors added fibroblast suspensions to collagen solutions and then allowed the collagen to gel into a native fibril lattice. Fibroblasts were found to migrate throughout the collagen gel lattice and shrink the lattice. 1,2 Lattice contraction served as a monitor of fibroblast activity, and this phenomenon has subsequently been used as an in vitro model of skin wound contraction. 2-4 One problem with the Bell model is that the initial seeding of the collagen gel with fibroblasts is homoge- neous with a high cell density in the range of 10 5 to 10 6 fibroblasts per milliliter of gel.5-6 The presence of such initially high fibroblast numbers is different from a real wound where fibroblast numbers are initially low at the wound site and increase after 3 to 4 days .' In the present study, we report on a new in vitro model for the examination of fibroblast activity in collagen gel lattices . The fibroblasts are initially packaged inside a tendon and subsequently allowed to grow out and multiply in the collagen gel. This produces a lag time before contraction of the collagen gel. This sequence of events more closely mimics the events of real wound contraction. Using a culture model containing two separated tendons, we studied the effect of initial tendon gap distance on the rate of collagen gel contraction and on the rate of fibroblast outgrowth into the collagen gel from the cut tendon ends

Metabolic Targeting of Lactate Efflux by Malignant Glioma Inhibits Invasiveness and Induces Necrosis: An In Vivo Study

Glioblastoma multiforme (GBM) are the most malignant among brain tumors. They are frequently refractory to chemotherapy and radiotherapy with mean patient survival of approximately 6 months, despite surgical intervention. The highly glycolytic nature of glioblastomas describes their propensity to metabolize glucose to lactic acid at an elevated rate. To survive, GBMs efflux lactic acid to the tumor microenvironment through transmembrane transporters denoted monocarboxylate transporters (MCTs). We hypothesized that inhibition of MCT function would impair the glycolytic metabolism and affect both glioma invasiveness and survival. We examined the effect on invasiveness with α-cyano-4-hydroxy-cinnamic acid (ACCA, 4CIN, CHCA), a small-molecule inhibitor of lactate transport, through Matrigel-based and organotypic (brain) slice culture invasive assays using U87-MG and U251-MG glioma cells. We then conducted studies in immunodeficient rats by stereotaxic intracranial implantation of the glioma cells followed by programmed orthotopic application of ACCA through osmotic pumps. Effect on the implanted tumor was monitored by small-animal magnetic resonance imaging. Our assays indicated that glioma invasion was markedly impaired when lactate efflux was inhibited. Convection-enhanced delivery of inhibitor to the tumor bed caused tumor necrosis, with 50% of the animals surviving beyond the experimental end points (3 months after inhibitor exhaustion). Most importantly, control animals did not display any adverse neurologic effects during orthotopic administration of ACCA to brain through programmed delivery. These results indicate the clinical potential of targeting lactate efflux in glioma through delivery of small-molecule inhibitors of MCTs either to the tumor bed or to the postsurgical resection cavity