Er,Yb:YVO4 waveguides deposited on amorphous SiO2 by PLD and UVPLD

In this work, erbium, and erbium and ytterbium co-doped YVO₄ waveguiding thin films were deposited on amorphous SiO₂ substrates by pulsed laser deposition (PLD) and ultraviolet-assisted pulsed laser deposition (UVPLD). The influence of the deposition technique on the structure, morphology, and optical properties of the films was investigated. At lower dopant concentrations the films prepared by UVPLD show better crystallinity and optical properties. All the samples show preferred orientation of the (001) zone axes parallel to the substrate surface. The polycrystalline samples show difference in the refractive indexes ?n (?n = n_TE − n_TM) for the TE and TM polarizations.     

Influence of bond defects on coiling of graphite

Abstract

The effect of annealing at 1400 ?C in argon on the bond structure of graphite ball milled for 100 h at 400 rpm in polar (water) and in non-polar (n-dodecane) liquids was investigated primarily by near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and transmission electron microscopy (TEM). Carbon K-edge NEXAFS allows the distortion of bonds in the hexagonal lattice to be investigated. It is shown that in-plane sp² bonds are strained and distorted after ball milling because sp³ bonds are introduced. Not surprisingly, annealing of the milled product restores sp² bonds but at the same time, coiling and formation of tube-like structures takes place. It is well established that graphite is not formed on annealing, and hence the results shown here demonstrate that the loss of sp³ carbons on annealing must proceed via a different mechanism by which they are formed by milling.     

The core protein of the chondroitin sulfate proteoglycan phosphacan is a high-affinity ligand of fibroblast growth factor-2 and potentiates its mitogenic activity

Using a radioligand binding assay we have demonstrated that phosphacan, a chondroitin sulfate proteoglycan of nervous tissue that also represents the extracellular domain of a receptor-type protein tyrosine phosphatase, shows saturable, reversible, high-affinity binding (Kd approximately 6 nM) to fibroblast growth factor-2 (FGF-2). Binding was reduced by only approximately 35% following chondroitinase treatment of the proteoglycan, indicating that the interaction is mediated primarily through the core protein rather than the glycosaminoglycan chains. Immunocytochemical studies also showed an overlapping localization of FGF-2 and phosphacan in the developing central nervous system. At concentrations of 10 microg protein/ml, both native phosphacan and the core protein obtained by chondroitinase treatment potentiated the mitogenic effect of FGF-2 (5 ng/ml) on NIH/3T3 cells by 75-90%, which is nearly the same potentiation as that produced by heparin at an equivalent concentration. Although studies on the role of proteoglycans in mediating the binding and mitogenic effects of FGF-2 have previously focused on cell surface heparan sulfate, our results indicate that the core protein of a chondroitin sulfate proteoglycan may also regulate the access of FGF-2 to cell surface signaling receptors in nervous tissue.     

Exponential stability of linear impulsive differential equations

In the present paper the notion of exponential stability for linear impulsive differential equations at fixed moments is made precise     

Effect of ball-milling on the rate and cycle-life performance of graphite as negative electrodes in lithium-ion capacitors

A commercial graphite is ball-milled and the pristine and ball-milled graphites are characterised for use as negative electrodes in lithium-ion capacitors (LICs). Ball milling graphite results in a decrease in discharge capacity when the charge rate is relatively slow, whereas, it leads to an increase in discharge capacity when the charge rate is high. When charged at 0.1 C, the discharge capacities of pristine, 3 h, 10 h and 30 h-milled materials at 6 C are 75, 69, 67 and 66% of theoretical capacity, respectively; however, when charged at 60 C, the discharge capacities of pristine, 3 h, 10 h and 30 h-milled materials, at 60 C, fall to 0.9, 13, 23 and 24% of theoretical capacity, respectively (theoretical capacity: 372 mAh g⁻¹, for LiC₆ stoichiometry). This difference in the discharge rate capability behaviour of the pristine and ball-milled graphites with charge rate is attributed to the interplay of two different charge storage mechanisms: Li-ion intercalation and Li-ion adsorption that co-exist; but the later becomes more significant for milled samples. In terms of cycle-life performance, pristine and ball-milled graphites follow similar trends observed for their rate capability behaviour.     

High affinity binding and overlapping localization of neurocan and phosphacan/protein-tyrosine phosphatase-zeta/beta with tenascin-R, amphoterin, and the heparin-binding growth-associated molecule

We have studied the interactions of the nervous tissue-specific chondroitin sulfate proteoglycans neurocan and phosphacan with the extracellular matrix protein tenascin-R and two heparin-binding proteins, amphoterin and the heparin-binding growth-associated molecule (HB-GAM), using a radioligand binding assay. Both proteoglycans show saturable, high affinity binding to tenascin-R with apparent dissociation constants in the 2-7 nM range. Binding is reversible, inhibited in the presence of unlabeled proteoglycan, and increased by approximately 60% following chondroitinase treatment of the proteoglycans, indicating that the interactions are mediated via the core (glyco)proteins rather than by the glycosaminoglycan chains, which may in fact partially shield the binding sites. In contrast to their interactions with tenascin-C, in which binding was decreased by approximately 75% in the absence of calcium, binding of phosphacan to tenascin-R was not affected by the absence of divalent cations in the binding buffer, although there was a small but significant decrease in the binding of neurocan. Neurocan and phosphacan are also high affinity ligands of amphoterin and HB-GAM (Kd = 0.3-8 nM), two heparin-binding proteins that are developmentally regulated in brain and functionally involved in neurite outgrowth. The chondroitin sulfate chains on neurocan and phosphacan account for at least 80% of their binding to amphoterin and HB-GAM. The presence of amphoterin also produces a 5-fold increase in phosphacan binding to the neural cell adhesion molecule contactin. Immunocytochemical studies showed an overlapping localization of the proteoglycans and their ligands in the embryonic and postnatal brain, retina, and spinal cord. These studies have therefore revealed differences in the interactions of neurocan and phosphacan with the two major members of the tenascin family of extracellular matrix proteins, and also suggest that chondroitin sulfate proteoglycans play an important role in the binding and/or presentation of differentiation factors in the developing central nervous system.